ci: publish docker images to a public registry

[sripwoud]

Is your feature request related to a problem? Please describe.
The images listed in the prod docker compose file require authentication.
Publishing public images would be more convenient and faster than having to build them myself for my own project.

Describe the solution you'd like
Publish docker images for at least the api to GH packages via a GH workflow.

Describe alternatives you've considered
Forking the repo, build what i need locally, push it to my fork. Which I did already

I am happy to write that workflow if you want