Automate release workflow

[Musholic]

Description of the problem being solved:

This automates some steps of the usual release workflow:

• Update the manifest version
• Update the manifest.xml hashes
• Add an automated check to ensure that the manifest file is up-to-date (correct hashes and version number)
  • Note that the checks are only run when the release PR is marked as ready for review. This is a workaround explained in https://github.com/peter-evans/create-pull-request/blob/main/docs/concepts-guidelines.md#workarounds-to-trigger-further-workflow-runs
• Automatically update master (fast-forward the merge commit into master) when the release PR is merged

The last manual step is to publish the release, it will automatically create the tag on the last commit of the master branch (the target branch of the release was changed to master, to avoid creating the release and tag on newly committed dev commits).

Includes a fix in tweak_changelogs.sh in the case where we removed the Release notes generated comment

Steps taken to verify a working solution:

• Tested on my fork
  • https://github.com/Musholic/PathOfBuilding-PoE2/pull/41 (the checks include the check_manifest check and the sync-release-to-master that was done automatically when closed)
  • I added the changelog.txt content on the merge commit description: https://github.com/Musholic/PathOfBuilding-PoE2/commit/7407c590b4be1d6b0614345faa169fe6c3173283