Release management: improve semantic versioning

[damyan]

Present tag $MAJOR_VERSION (in this case: v2) pointing to the last released version. In that case all action consumers can stick to the v2 version, without needing to keep track of version changes with dependabot and updating their caller actions each time.

See also https://docs.github.com/en/actions/creating-actions/about-custom-actions#using-tags-for-release-management for details.