Release 0.22

[yara-blue]

Little todo list to track this. Releasing 0.22 also unblocks #831

• Updated upgrade guide
• Write something for the RustAudio discord and maybe Rust reddit
• Go through the release procedure https://github.com/RustAudio/rodio/blob/master/CONTRIBUTING.md#release-procedure
• Post in RustAudio and maybe Reddit

[yara-blue]

@roderickvd Shall I get on this tomorrow?

[roderickvd]

Sure thing!