Create combined workflow for WordPress plugins

[carstingaxion]

### Tasks
- [ ] [swissspidy/wp-plugin-check-action: Test your WordPress plugin with Plugin Check](https://github.com/swissspidy/wp-plugin-check-action) (***see*** [wp-plugin-check-action.yml](https://github.com/figuren-theater/theater-production-blocks/actions/workflows/wp-plugin-check-action.yml))
- [ ] ...
- [ ] [Playground Comment Worker](https://gist.github.com/jdevalk/62d523be19743fd495144ade4c65e54c)
- [ ] https://github.com/swissspidy/wp-performance-action
- [ ] https://github.com/marketplace/actions/wordpress-version-checker
- [ ] https://github.com/marketplace/actions/wordpress-plugin-readme-md-validator

[carstingaxion]

https://make.wordpress.org/core/2020/10/15/introducing-github-actions-for-automated-testing/

[carstingaxion]

https://joost.blog/github-actions-wordpress/