[Example] Add franken php runtime

[alexander-schranz]

What's in this PR?

Shows an example how to run Sulu with FrankenPHP.

More on our Blog: https://sulu.io/blog/running-sulu-with-frankenphp

Requires currently a custom build:

docker build -t custom-franken-php .

Update the .env.local to allow connection inside docker to host:

DATABASE_URL=mysql://root:ChangeMe@host.docker.internal:3306/su_demo?serverVersion=8.0
ELASTICSEARCH_HOST=host.docker.internal:9200
REDIS_HOST=host.docker.internal:6379

Run the Dockerimage:

docker run -e FRANKENPHP_CONFIG="worker ./public/index.php" -v $PWD:/app -p 80:80 -p 443:443 custom-franken-php

open https://localhost/