Publish-release workflow will run for non-release branches

[jsoberg]

Hey! I was using your workflows as a template and noticed that the publish release workflow will run and fail for any non-release PR that's merged in (failing because it doesn't match the expected release/<version> branch name when trying to parse the version). We could add a startsWith check to the if block at the beginning to skip the workflow if the merging branch isn't a release/<version> branch; I'll put in a quick PR with what I used if you'd like to look.

Thanks for all the great workflows!