Automate the release process

[mjakl]

The release process at the moment is manual, i.e. the release engineer needs to supply a version. Using Changesets as described in #12, it should be possible to make semver conform releases automatially.

The current GitHub Action does not change the repository (i.e. tag release versions or add/change files like a changelog). Tagging and updating the respective changelog would be nice and should be included in the automated release process.