Provide docker image/suite

[MTRNord]

Some docker files would be nice to make deployment easier.

For now only the server. Later also a docker compose for pg14, the server and then a Web interface

[MTRNord]

Dockerfile now exists and works.

Running can be done using something along the lines of docker run -v /etc/erooster/config.yml:/config.yml coreharbor.kubernetes.midnightthoughts.space/erooster/erooster:latest

Missing is a) what needs to be mounted and b) testing pg

After that, we probably should provide a docker-compose.yml