Post-release: alpha branch detection; master sync about newspack-scripts

[adekbadek]

This was caused by not persisting the files to workspace in the CI configuration of the repository using newspack-scripts (newspack-plugin in this case). After the release job of the CI, the files should be persisted with a persist_to_workspace directive, so the project state is the same for the post-release step is the same as at the end of the release step.

After the persist_to_workspace directive is added, I'll do the following for each repository:

1. Reset alpha on top of release (which should have happened post-release)
2. Manual alpha release, since GH merge does not allow to choose a merge strategy:
   git co alpha && git merge master --strategy-option=ours