Mimics the behaviour of the 'deploy-release' workflow, even though branch deployment doesn't depend on Pico's tests to succeed. Pull requests still use the 'test' workflow directly.
Since Travis CI was transformed into a proprietary service we didn't have a CI pipeline. This heavily refactors and simplifies the CI pipeline and uses GitHub Actions to deploy new Pico releases. You can use Pico's Makefile to build new releases locally, too. Pico's build script no longer depends on any external resources (like our `picocms/ci-tools` collection). However, this isn't true for other release deployment steps, like updating phpDoc class docs, version badge, cloc stats, etc., even though the CI scripts are mostly self-containing now.
After resolving a issue, we usually keep it open for about a week to give users some more time for feedback and further questions. This is especially true for issues with the `type: Notice`, `type: Question`, `type: Discussion` and `type: Invalid` labels. After 7 days with no interaction, [Probot](https://probot.github.io/)'s [Stale](https://probot.github.io/apps/stale/) bot (@probot-stale) adds the `info: Stale` label to the issue to ask the participants whether the issue has been resolved. If no more activity occurs, the issue will be automatically closed by @probot-stale 2 days later.
Daniel Rudolf