FIx an issue with using an empty tag for releases

What's Changed

Instead of using $GITHUB_REF (which can be empty) let's rely on github.event.release.tag_name:

  Event received: 'release' (with a reference '' / tag name 'v3.13.5-8.4.10')
  Tagging with 3.13.5-8.4.10

---

• Update action.yml: use github.ref by @macbre in #46
• Update action.yml: use github.event instead by @macbre in #47

Full Changelog: v15...v16