Add support for Protocol 22

[Shaptic]

All of these PRs have already been reviewed:

• #769
• #774
• #770

This just merges the feature branch into master and makes npm publishing use the beta tag for RC purposes.

[github-actions[bot]]

Size Change: +46.2 kB (+1.44%)

Total Size: 3.26 MB

Filename	Size	Change
dist/stellar-base.js	2.39 MB	+35.5 kB (+1.51%)
dist/stellar-base.min.js	868 kB	+10.7 kB (+1.25%)

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