Create conda env for sphinx #34

Job	Run time
build_linux (3.8)	5m 35s
build_linux (3.9)	11m 19s
build_linux (3.10)	7m 40s
build_windows (3.8)	9m 27s
build_windows (3.9)	15m 36s
build_windows (3.10)	9m 31s
test_linux (3.8, true, ubuntu-20.04)	3m 17s
test_linux (3.9, true, ubuntu-20.04)	1m 26s
test_linux (3.10, true, ubuntu-20.04)	2m 30s
upload_linux	0s
test_windows (3.8, false, windows-latest)	6m 27s
test_windows (3.9, false, windows-latest)	7m 0s
test_windows (3.10, false, windows-latest)	5m 28s
upload_windows	0s
	1h 25m 16s

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