Releases workflow improvements for app-sdk

[lkostrowski]

1. Prepare pre-release workflow (https://github.com/changesets/changesets/blob/main/docs/prereleases.md) for branches opened by changesets. This should be automatically creating RCs and attach them to the PR
2. Create label "skip release" and modify existing "dev" releases to stop, if the branch exists (reason for that is some chore PR that automatically releases NPM packages with no diff)