Setup CI for building releases

[jonasKjellerup]

Whenever a push to the release branch occurs we want a GitHub action to run with the following results:

• The project should be built and zipped, such that it is ready for deployment.
• The songbook should additionally be zipped on its own.
• A tag should be created with the aforementioned uploaded.

Additionally a GitHub action should check for the following, when merge requests into release are created:

• That the version tag has been updated.
• A changelog for said version exists.