Note supported platform versions #373

Job	Run time
Test (ubuntu-latest)	58s
MinimalVersions (ubuntu-latest)	21s
Test (macos-latest)	1m 8s
Test (windows-latest)	2m 8s
MinimalVersions (macos-latest)	38s
CheckTargets	1m 10s
Check (armv7-sony-vita-newlibeabihf)	31s
MinimalVersions (windows-latest)	44s
Check (sparcv9-sun-solaris)	31s
Clippy	9s
Docs	16s
Check (x86_64-pc-solaris)	32s
MSRV (ubuntu-latest)	12s
Rustfmt	8s
MSRV (macos-latest)	22s
Nightly	22s
MSRV (windows-latest)	30s
Sanitizer (address)	1m 6s
Sanitizer (leak)	49s
TestPoll	30s
Sanitizer (memory)	1m 38s
TestWakerPipe	38s
Sanitizer (thread)	56s
Passed	1s
	16m 18s

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