Add documentation for multiband #370

Job	Run time
Tests on other platforms (windows-2019, 3.10)	4m 11s
Tests on paywalled platforms	0s
Tests on other platforms (windows-2022, 3.11)	3m 16s
Tox test (py38)	3m 27s
Tests on other platforms (windows-2022, 3.12)	3m 57s
Tox test (py39)	3m 12s
Tests on other platforms (macos-12, 3.11)	3m 6s
Tox test (py310)	3m 15s
Tests on other platforms (macos-13, 3.12)	4m 38s
Tox test (py311)	3m 4s
Tox test (py312-cover)	6m 30s
Tox test (docs, graphviz)	1m 42s
Docker image	0s
PyPI packaging	0s
	40m 18s

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