add scipy-stubs as non-typeshed stub package

[jorenham]

SciPy itself has no py.typed and barely any stubs, so I wrote scipy-stubs. Recently, it has been accepted as an official scipy project.
This stubs-only package is complete (no untyped) and valid (according to mypy, stubtest, pyright, basedmypy and basedpyright), and carefully annotated (by humans).
And for what it's worth, it's also on the list of mypy_primer projects.

I'm open to any feedback, questions, and ideas in general; no need to hold back :)

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

imagehash (https://github.com/JohannesBuchner/imagehash)
- imagehash/__init__.py:273: error: Cannot find implementation or library stub for module named "scipy.fftpack"  [import-not-found]
+ imagehash/__init__.py:273: error: Library stubs not installed for "scipy.fftpack"  [import-untyped]
+ imagehash/__init__.py:273: note: Hint: "python3 -m pip install scipy-stubs"
+ imagehash/__init__.py:273: note: (or run "mypy --install-types" to install all missing stub packages)
- imagehash/__init__.py:273: error: Cannot find implementation or library stub for module named "scipy"  [import-not-found]
+ imagehash/__init__.py:273: error: Library stubs not installed for "scipy"  [import-untyped]

streamlit (https://github.com/streamlit/streamlit)
- lib/tests/streamlit/web/server/oidc_mixin_test.py:23:1: note: (or run "mypy --install-types" to install all missing stub packages)
- lib/tests/streamlit/elements/audio_test.py:216:1: error: Cannot find implementation or library stub for module named "scipy.io"  [import-not-found]
+ lib/tests/streamlit/elements/audio_test.py:216:1: error: Library stubs not installed for "scipy.io"  [import-untyped]
+ lib/tests/streamlit/elements/audio_test.py:216:1: note: Hint: "python3 -m pip install scipy-stubs"
+ lib/tests/streamlit/elements/audio_test.py:216:1: note: (or run "mypy --install-types" to install all missing stub packages)

arviz (https://github.com/arviz-devs/arviz)
- arviz/stats/ecdf_utils.py:8: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
- arviz/stats/ecdf_utils.py:9: error: Cannot find implementation or library stub for module named "scipy.optimize"  [import-not-found]
+ arviz/stats/ecdf_utils.py:8: error: Library stubs not installed for "scipy.stats"  [import-untyped]
+ arviz/stats/ecdf_utils.py:9: error: Library stubs not installed for "scipy.optimize"  [import-untyped]
- arviz/stats/density_utils.py:6: error: Cannot find implementation or library stub for module named "scipy.fftpack"  [import-not-found]
- arviz/stats/density_utils.py:7: error: Cannot find implementation or library stub for module named "scipy.optimize"  [import-not-found]
- arviz/stats/density_utils.py:8: error: Cannot find implementation or library stub for module named "scipy.signal"  [import-not-found]
- arviz/stats/density_utils.py:9: error: Cannot find implementation or library stub for module named "scipy.signal.windows"  [import-not-found]
- arviz/stats/density_utils.py:10: error: Cannot find implementation or library stub for module named "scipy.sparse"  [import-not-found]
- arviz/stats/density_utils.py:11: error: Cannot find implementation or library stub for module named "scipy.special"  [import-not-found]
+ arviz/stats/density_utils.py:6: error: Library stubs not installed for "scipy.fftpack"  [import-untyped]
+ arviz/stats/density_utils.py:7: error: Library stubs not installed for "scipy.optimize"  [import-untyped]
+ arviz/stats/density_utils.py:8: error: Library stubs not installed for "scipy.signal"  [import-untyped]
+ arviz/stats/density_utils.py:9: error: Library stubs not installed for "scipy.signal.windows"  [import-untyped]
+ arviz/stats/density_utils.py:10: error: Library stubs not installed for "scipy.sparse"  [import-untyped]
+ arviz/stats/density_utils.py:11: error: Library stubs not installed for "scipy.special"  [import-untyped]
- arviz/stats/stats_utils.py:10: error: Cannot find implementation or library stub for module named "scipy.fftpack"  [import-not-found]
- arviz/stats/stats_utils.py:11: error: Cannot find implementation or library stub for module named "scipy.interpolate"  [import-not-found]
- arviz/stats/stats_utils.py:12: error: Cannot find implementation or library stub for module named "scipy.stats.mstats"  [import-not-found]
+ arviz/stats/stats_utils.py:10: error: Library stubs not installed for "scipy.fftpack"  [import-untyped]
+ arviz/stats/stats_utils.py:11: error: Library stubs not installed for "scipy.interpolate"  [import-untyped]
+ arviz/stats/stats_utils.py:12: error: Library stubs not installed for "scipy.stats.mstats"  [import-untyped]
- arviz/stats/stats.py:11: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
- arviz/stats/stats.py:11: error: Cannot find implementation or library stub for module named "scipy"  [import-not-found]
+ arviz/stats/stats.py:11: error: Library stubs not installed for "scipy.stats"  [import-untyped]
+ arviz/stats/stats.py:11: error: Library stubs not installed for "scipy"  [import-untyped]
- arviz/stats/stats.py:14: error: Cannot find implementation or library stub for module named "scipy.optimize"  [import-not-found]
+ arviz/stats/stats.py:14: error: Library stubs not installed for "scipy.optimize"  [import-untyped]
- arviz/stats/diagnostics.py:9: error: Cannot find implementation or library stub for module named "scipy"  [import-not-found]
+ arviz/stats/diagnostics.py:9: error: Library stubs not installed for "scipy"  [import-untyped]
- arviz/plots/plot_utils.py:11: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
- arviz/plots/plot_utils.py:12: error: Cannot find implementation or library stub for module named "scipy.interpolate"  [import-not-found]
+ arviz/plots/plot_utils.py:11: error: Library stubs not installed for "scipy.stats"  [import-untyped]
+ arviz/plots/plot_utils.py:12: error: Library stubs not installed for "scipy.interpolate"  [import-untyped]
- arviz/plots/parallelplot.py:4: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
- arviz/plots/loopitplot.py:4: error: Cannot find implementation or library stub for module named "scipy"  [import-not-found]
- arviz/plots/hdiplot.py:6: error: Cannot find implementation or library stub for module named "scipy.interpolate"  [import-not-found]
- arviz/plots/hdiplot.py:7: error: Cannot find implementation or library stub for module named "scipy.signal"  [import-not-found]
- arviz/plots/ecdfplot.py:6: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ arviz/plots/parallelplot.py:4: error: Library stubs not installed for "scipy.stats"  [import-untyped]
+ arviz/plots/loopitplot.py:4: error: Library stubs not installed for "scipy"  [import-untyped]
+ arviz/plots/hdiplot.py:6: error: Library stubs not installed for "scipy.interpolate"  [import-untyped]
+ arviz/plots/hdiplot.py:7: error: Library stubs not installed for "scipy.signal"  [import-untyped]
+ arviz/plots/ecdfplot.py:6: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- examples/matplotlib/mpl_styles.py:10: error: Cannot find implementation or library stub for module named "scipy"  [import-not-found]
+ examples/matplotlib/mpl_styles.py:10: error: Library stubs not installed for "scipy"  [import-untyped]
- examples/matplotlib/mpl_plot_ecdf_comparison.py:8: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ examples/matplotlib/mpl_plot_ecdf_comparison.py:8: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- examples/matplotlib/mpl_plot_ecdf.py:9: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ examples/matplotlib/mpl_plot_ecdf.py:9: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- examples/bokeh/bokeh_plot_ecdf_comparison.py:7: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
- examples/bokeh/bokeh_plot_ecdf.py:6: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ examples/bokeh/bokeh_plot_ecdf_comparison.py:7: error: Library stubs not installed for "scipy.stats"  [import-untyped]
+ examples/bokeh/bokeh_plot_ecdf.py:6: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- asv_benchmarks/benchmarks/benchmarks.py:5: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ asv_benchmarks/benchmarks/benchmarks.py:5: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- arviz/tests/base_tests/test_stats_utils.py:7: error: Cannot find implementation or library stub for module named "scipy.special"  [import-not-found]
- arviz/tests/base_tests/test_stats_utils.py:8: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
- arviz/tests/base_tests/test_stats_ecdf_utils.py:4: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
- arviz/tests/base_tests/test_stats_ecdf_utils.py:4: error: Cannot find implementation or library stub for module named "scipy"  [import-not-found]
+ arviz/tests/base_tests/test_stats_utils.py:7: error: Library stubs not installed for "scipy.special"  [import-untyped]
+ arviz/tests/base_tests/test_stats_utils.py:8: error: Library stubs not installed for "scipy.stats"  [import-untyped]
+ arviz/tests/base_tests/test_stats_ecdf_utils.py:4: error: Library stubs not installed for "scipy.stats"  [import-untyped]
+ arviz/tests/base_tests/test_stats_ecdf_utils.py:4: error: Library stubs not installed for "scipy"  [import-untyped]
- arviz/tests/base_tests/test_diagnostics.py:10: error: Cannot find implementation or library stub for module named "scipy"  [import-not-found]
+ arviz/tests/base_tests/test_diagnostics.py:10: error: Library stubs not installed for "scipy"  [import-untyped]
- arviz/plots/backends/matplotlib/mcseplot.py:5: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ arviz/plots/backends/matplotlib/mcseplot.py:5: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- arviz/plots/backends/matplotlib/essplot.py:5: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ arviz/plots/backends/matplotlib/essplot.py:5: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- arviz/plots/backends/matplotlib/bpvplot.py:5: error: Cannot find implementation or library stub for module named "scipy"  [import-not-found]
+ arviz/plots/backends/matplotlib/bpvplot.py:5: error: Library stubs not installed for "scipy"  [import-untyped]
- arviz/plots/backends/bokeh/mcseplot.py:7: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ arviz/plots/backends/bokeh/mcseplot.py:7: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- arviz/plots/backends/bokeh/essplot.py:6: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ arviz/plots/backends/bokeh/essplot.py:6: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- arviz/tests/base_tests/test_utils.py:8: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
- arviz/tests/base_tests/test_utils.py:8: error: Cannot find implementation or library stub for module named "scipy"  [import-not-found]
+ arviz/tests/base_tests/test_utils.py:8: error: Library stubs not installed for "scipy.stats"  [import-untyped]
+ arviz/tests/base_tests/test_utils.py:8: error: Library stubs not installed for "scipy"  [import-untyped]
- arviz/tests/base_tests/test_stats.py:12: error: Cannot find implementation or library stub for module named "scipy.special"  [import-not-found]
- arviz/tests/base_tests/test_stats.py:13: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ arviz/tests/base_tests/test_stats.py:12: error: Library stubs not installed for "scipy.special"  [import-untyped]
+ arviz/tests/base_tests/test_stats.py:13: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- arviz/tests/base_tests/test_plots_matplotlib.py:14: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ arviz/tests/base_tests/test_plots_matplotlib.py:14: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- arviz/tests/base_tests/test_plots_bokeh.py:8: error: Cannot find implementation or library stub for module named "scipy.stats"  [import-not-found]
+ arviz/tests/base_tests/test_plots_bokeh.py:8: error: Library stubs not installed for "scipy.stats"  [import-untyped]
- arviz/plots/backends/bokeh/bpvplot.py:6: error: Cannot find implementation or library stub for module named "scipy"  [import-not-found]
+ arviz/plots/backends/bokeh/bpvplot.py:6: error: Library stubs not installed for "scipy"  [import-untyped]
+ arviz/plots/backends/bokeh/bpvplot.py:6: note: Hint: "python3 -m pip install scipy-stubs"

AutoSplit (https://github.com/Toufool/AutoSplit)
- src/compare.py:8:1: error: Skipping analyzing "scipy": module is installed, but missing library stubs or py.typed marker  [import-untyped]
+ src/compare.py:8:1: error: Library stubs not installed for "scipy"  [import-untyped]
+ src/compare.py:8:1: note: Hint: "python3 -m pip install scipy-stubs"