Prepare release 0.2.1 #2182

Job	Run time
Lint	30s
Test (stable, windows-latest)	1m 18s
Test (stable, ubuntu-latest)	27s
Test feature matrix	11m 18s
Test (stable, macos-latest)	29s
MSRV	21s
Documentation	29s
Test FFI (stable, ubuntu-latest)	39s
	15m 31s

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