Prepare release 0.2.1 (#706) #2183

Job	Run time
Lint	30s
Documentation	33s
Test feature matrix	10m 57s
Test (stable, ubuntu-latest)	33s
Test (stable, windows-latest)	1m 29s
MSRV	22s
Test (stable, macos-latest)	54s
Test FFI (stable, ubuntu-latest)	32s
	15m 50s

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