feat: Shared publish gem workflow

[jonrandahl]

Introduces a reusable GitHub Actions workflow to automate the process of building, releasing, and publishing Ruby gems, standardising the release pipeline for projects.

What's changed:

• A new GitHub Actions workflow for releasing and publishing gems was added.
• Automated detection of the project's specified Ruby version for consistent builds was implemented.
• The gem build process was integrated into the automated pipeline.
• GitHub releases are now automatically created, including generated release notes and the gem artefact.
• The built gem is automatically published to a package registry following a successful release.