Create conda env for sphinx #55

Job	Run time
build_windows (3.8)	11m 18s
build_linux (3.8)	1m 54s
build_windows (3.9)	7m 41s
build_linux (3.9)	3m 33s
build_windows (3.10)	7m 6s
build_linux (3.10)	3m 22s
test_linux (3.8, true, ubuntu-20.04)	1m 49s
test_linux (3.9, true, ubuntu-20.04)	2m 8s
test_linux (3.10, true, ubuntu-20.04)	1m 56s
upload_linux	0s
test_windows (3.8, false, windows-latest)	6m 38s
test_windows (3.9, false, windows-latest)	6m 11s
test_windows (3.10, false, windows-latest)	5m 46s
upload_windows	0s
	59m 22s

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