Configure github "environments"

[cfoellmann]

We should try and automate "stuff" with the new github feature environments.

• github-pages generate github pages (@blueglassdigital you should activate it via the repo settings and let it create the gh-pages branch if you want the pages for now or the future)

• code-quality test PRs for code quality and later php unit tests (I like scrutinizer-ci.com for this as an example)

• deploy-wporg deploy to wp.org SVN via the github pipeline (including testing for all needed changes like version numbers and minified assets)

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Lets use GitHub actions. Potential solutions:

• https://10up.com/blog/2019/introducing-github-actions-for-wordpress-plugins/ | https://github.com/10up/actions-wordpress/

• https://github.com/lubusIN/actions/tree/master/wordpress