Infra: Create GitHub Releases on npm release

[ryan-roemer]

We now only have single tags for releases with our custom git tagging strategy. It would be nice to have real GH releases again.

Options:

• [ ] See if https://github.com/changesets/action/pull/193 for changesets (adding createGithubReleases) works for us with our custom git tagging scheme.
• [ ] Do it ourselves with maybe a separate action keyed on a git tag happening using something like https://github.com/softprops/action-gh-release
  • [ ] We'll need to ingest changelogs probably in a custom script to generate release notes.