initial readme.md #7

Job	Run time
Formatting	15s
Building (nightly, windows-latest)	1m 35s
Building (stable, macOS-latest)	42s
Building (nightly, ubuntu-latest)	46s
Building (stable, ubuntu-latest)	48s
Linting	28s
Building (nightly, macOS-latest)	1m 2s
Building (stable, windows-latest)	1m 55s
	7m 31s

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