Use Github Actions release automation

[mattwynne]

🤔 What's the problem you've observed?

We're still using the old-school mechanism of a Make target with the release script running locally on a developer workstation.

✨ Do you have a proposal for making it better?

Implement a release-ruby.yml github action, similar to https://github.com/cucumber/cucumber-ruby/blob/main/.github/workflows/cucumber-ruby.yml using a protected release branch, with a protected environment secret.

📚 Any additional context?

We need a guide to reference here!

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[mattwynne]

OK this is done. v2.6.1 was released by Github Actions.

@luke-hill ping me if you want a walk-through of how to make a release, it should be really straightforward once you've installed polyglot-release.