Resolves #394

These changes add a new workflow for publishing the plugin site. It runs when:

• a GitHub release is published
• the workflow is manually executed (on https://github.com/wvengen/proguard-maven-plugin/actions/workflows/site.yml, once this pull request is merged)

Additionally, every CI build also builds the plugin site (but does not deploy it) to make sure that building it works, and to avoid any surprises when trying to create a release.

Here is an example of the new site: https://marcono1234.github.io/proguard-maven-plugin/index.html

If you want anything changed, please let me know.

Open tasks for you as maintainers:

• On https://github.com/wvengen/proguard-maven-plugin/settings/pages change the source to "GitHub Actions"
• On https://github.com/wvengen/proguard-maven-plugin/settings/environments possibly add protection rules for the newly created github-pages environment, as suggested by https://github.com/actions/deploy-pages?tab=readme-ov-file#security-considerations
  • Note: If you want to keep the on: release of the workflow setup in this pull request, then it seems you also need to not only add the master branch as allowed, but also a wildcard for tags, e.g. v* (but requires consistent tag naming, or just any tags with *?)
    And maybe you want to also protect those v* tags (or just any tags with *?) under https://github.com/wvengen/proguard-maven-plugin/settings/tag_protection then