DOC: initial sphinx and readthedocs stub #395

Job	Run time
publish-on-pypi	1m 45s
build-installer-on-windows / build	24m 26s
build-on-macos / build	1s
build-on-ubuntu / build	4m 51s
build-on-windows / build	31m 8s
publish-on-github	0s
	1h 2m 11s

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