Use Actions to build and publish Docker images to Github Container Registry

[toffee-makes-things]

See #1003

[sudokoko]

I've approved check runs, if these are successful I will review after work.

[toffee-makes-things]

also on pull requests IIRC before a merge the Docker workflow does not push to the github container registry, just builds to make sure it works, after merge the workflow reruns and pushes to container registry

[toffee-makes-things]

if this workflow is merged to main

you should be able to run something like this docker pull ghcr.io/LBPUnion/projectlighthouse:main and get the docker image for the latest commit

[sudokoko]

prelim review

[sudokoko]

Second wave of nitpicks, otherwise looks mostly good.

[toffee-makes-things]

Done @sudokoko, ignore that one commit message being messed up, phone keyboard did a stupid

[Zaprit]

Looks good for the most part, main thing is building ARM images.

[toffee-makes-things]

@Zaprit all done