Is there a Basic GateKeeper Docker or Docker-Compose tutorial?

Hi,
I’m trying to build a docker-compose based proof of concept to show how Gatekeeper works.
Is there any documentation or tutorial about using this image https://hub.docker.com/r/keycloak/keycloak-gatekeeper with an existing configuration yml file?
Is there also an advanced documentation about how to use regexp in such a file?
Thanks.