GitHub container registry for the the project

[nightred]

I am requesting that this project off the docker image in the GitHub container registry.

The change would make the container pullable from ghcr.io/RimworldTogether/Rimworld-Together

This change would mean that server operators would not need to pull the project and build the docker container before usage.

Currently when pulling the image the following error is given: docker: Error response from daemon: Head "https://ghcr.io/v2/rimworldtogether/rimworld-together/manifests/latest": unauthorized.