Make port config and exposure in docker configurable

[zbisch]

• Make port config and exposure in docker configurable: I suggest removing the EXPOSE line from the Dockerfile, make the port configurable via an environmental variable, and then update the docker-compose file to expose and map the port to a port on the host machine.
• Maybe remove "--env-file", "../../example.env" from the CMD line? Or add a line to the docker compose file that updates the command to run (and adds the example.env