Create conda env for sphinx #32

Job	Run time
build_linux (3.8)	5m 26s
build_windows (3.8)	16m 6s
build_linux (3.9)	8m 23s
build_windows (3.9)	14m 56s
build_linux (3.10)	5m 55s
build_windows (3.10)	12m 9s
test_linux (3.8, true, ubuntu-20.04)	1m 20s
test_linux (3.9, true, ubuntu-20.04)	1m 33s
test_linux (3.10, true, ubuntu-20.04)	2m 38s
upload_linux	0s
test_windows (3.8, false, windows-latest)	8m 32s
test_windows (3.9, false, windows-latest)	5m 8s
test_windows (3.10, false, windows-latest)	4m 55s
upload_windows	0s
	1h 27m 1s

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