Implement CI for releases

[leograba]

As of today, I am doing releases locally in a clumsy way:

• Update the release tag on Docker Compose and VS Code config files
• Add release commit and tag
• Rebuild and push the containers locally with the new tag

But the release process should be automated to avoid me missing steps or making mistakes.

[leograba]

A big chunk of this ticket's goal has been implemented as part of #25

It automates the process of updating the release version, commit and tag, and then open a PR.

The next steps will be to improve the test pipeline, and implement steps to build (or re-tag rc) the final containers.