Docker image #179

Hey,

I am thinking about running overmind in my Docker image as an entrypoint to run a few other programs.
It would be nice if there would be a docker image, where I could copy the binary out.
kinda:

COPY --from=ghcr.io/DarthSim/overmind:latest /overmind /usr/local/bin/overmind

I can provide a PR if this is wanted :)