Add make.bat for building on Windows (#971) #918

Job	Run time
build (3.7, 4.0.3)	13s
build (3.7, 4.1.2)	19s
build (3.7, 4.2.0)	13s
build (3.7, 4.3.2)	13s
build (3.7, 4.5.0)	11s
build (3.7, 5.0.2)	12s
build (3.7, 5.1.1)	12s
build (3.7, 5.3.0)	11s
build (3.8, 4.0.3)	12s
build (3.8, 4.1.2)	14s
build (3.8, 4.2.0)	15s
build (3.8, 4.3.2)	13s
build (3.8, 4.5.0)	24s
build (3.8, 5.0.2)	15s
build (3.8, 5.1.1)	14s
build (3.8, 5.3.0)	15s
build (3.8, 6.1.3)	16s
build (3.8, git+https://github.com/sphinx-doc/sphinx.git@master)	10s
build (3.9, 4.0.3)	13s
build (3.9, 4.1.2)	18s
build (3.9, 4.2.0)	17s
build (3.9, 4.3.2)	15s
build (3.9, 4.5.0)	13s
build (3.9, 5.0.2)	23s
build (3.9, 5.1.1)	13s
build (3.9, 5.3.0)	14s
build (3.9, 6.1.3)	17s
build (3.9, git+https://github.com/sphinx-doc/sphinx.git@master)	9s
build (3.10, 4.2.0)	19s
build (3.10, 4.3.2)	14s
build (3.10, 4.5.0)	16s
build (3.10, 5.0.2)	12s
build (3.10, 5.1.1)	21s
build (3.10, 5.3.0)	16s
build (3.10, 6.1.3)	15s
build (3.10, git+https://github.com/sphinx-doc/sphinx.git@master)	23s
	9m 0s

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