Use Actions to publish already built Docker images to Github Container Registry

[toffee-makes-things]

As the title says, later i'll mess around and create a workflow file for this and make a PR

I don't know if you guys use Docker internally (though i would assume so considering the Dockerfile) but if you do this should be quite useful so you (or anyone else) can pull an already built (like a minute or two after commit) image from GitHub as apposed to making a new docker build on device every time you have a change.

[toffee-makes-things]

made a pr #1004

[toffee-makes-things]

pr #1004 merged