Update the license file to mention parts of the code are under the PSF license.

Author: ronaldoussoren

Diff for: License.rst

@@ -0,0 +1,24 @@
+License
+=======
+
+Copyright (c) 2020 Ronald Oussoren, licensed under the MIT license.
+
+Parts of the code were copied from the stdlib implemenation of asyncio and are licensed under
+the PSF license.
+
+
+MIT License
+...........
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+and associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do
+so.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

Diff for: pyproject.toml

@@ -15,11 +15,14 @@ requires-python = ">=3.7,<4"
 classifiers = [
     "Intended Audience :: Developers",
     "License :: OSI Approved :: MIT License",
+    "License :: OSI Approved :: Python Software Foundation License",
     "Operating System :: MacOS :: MacOS X",
+    "Framework :: AsyncIO",
     "Programming Language :: Python :: 3 :: Only",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3.7",
     "Programming Language :: Python :: 3.8",
+    "Programming Language :: Python :: 3.9",
     "Topic :: Software Development :: Libraries :: Python Modules",
     "Development Status :: 4 - Beta",
 ]