* Improve GHA build process to provide scoped Docker images for PHP 7.3-8.0
* Push cached build layers to Docker Hub instead of ghcr.io
* Build "-secured" Docker image
* Run Docker publish workflow for the "experimental-scoped" branch
* Use "plain" progress output from buildx
* Build only one image named "secured", based on PHP 8.0
This is the rector configuration file for developing on rector itself, and should not be used in runtime.
Without this change, the docker image (which runs with `/rector` as its working directory) would use this `rector.yaml` as the default configuration file. This leads to unexpected effects, such as rector ignoring any `tests/`-directory by default.
