ENH: Convert README from ReStructured Text to MarkDown #232

Job	Run time
build-linux-python-packages (39)	3m 58s
build-test-cxx (ubuntu-22.04)	8m 32s
build-linux-python-packages (310)	6m 3s
build-windows-python-packages (9)	7m 43s
build-test-cxx (windows-2022)	15m 39s
build-macos-python-packages (9)	1s
build-linux-python-packages (311)	3m 47s
build-windows-python-packages (10)	9m 29s
build-test-cxx (macos-13)	10m 43s
build-macos-python-packages (10)	6m 42s
build-windows-python-packages (11)	11m 25s
build-test-cxx (macos-14)	6m 31s
build-macos-python-packages (11)	1s
	1h 30m 34s

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