Show link to changelog in the docs

[ccremer]

Summary

• This will display a link in the navigation pointing to GitHub release, but only when the Antora component was built from a tag in the playbook (not master for example), see https://docs.antora.org/antora/2.3/page/intrinsic-attributes/#page-attributes

Checklist

• Keep pull requests small so they can be easily reviewed.
• Categorize the PR by setting a good title and adding one of the labels:
  bug, enhancement, documentation, change, breaking,
  as they show up in the changelog
• Update the documentation.

[tobru]

Cool. Never used that before, let's see how this works when we tagged the release.