* Rootless Dockerfile/Optimized build
Add unneeded files to .dockerignore
Split Dockerfile into more stages to allow Composer/Yarn to run concurrently
Don't log supervisord to a file, as file logging in a Docker container makes no sense
Redirect process output to container output for log processors
Run all processes as non-root
Minimize files with write permission for non-root user
Move docker folder out of .github, as it has nothing to do with GitHub
* Remove install-php-extensions utility after use and name final stage
* Test arm64 runner
* Allow Docker workflow caching multi-arch separately
* Fix Docker publish workflow branches
* Move Caddyfile/crontab config into docker directory, remove redundant supervisord user
* Further restrict permissions
* Supervisord logs
