Dockerize the chat runtime

[JKrag]

It seems a bit pointless to just Dockerize the tool itself, as you would still need a shell to run it, and thus only avoid installing Git. A more interesting idea could be to make it self-contained in the sense that the Docker container entrypoint would take a remote git URI as an argument, and would then clone the chat repo internally every time, so it would be self-contained and not leave any residue on the file system once the container is deleted.