rtc-v0.22.0

What's Changed

• remove AudioFrame.remix_and_resample by @theomonnom in #385
• remove ChatManager by @theomonnom in #387
• serialize VideoBufferType using human-readable str by @theomonnom in #392
• better track types by @theomonnom in #393
• update CI to use protobuf 4.x by @davidzhao in #396
• version bump 0.22 by @davidzhao in #397

Full Changelog: rtc-v0.21.3...rtc-v0.22.0