Upload container image to GHCR in addtion to Docker Hub

### Description

I've primarily used GHCR for most of my Docker compose files.

It's also good to have an additional mirror the container can be pulled from, as at the time of writing Docker Hub is dead.

Start by locating the repository's current Docker Hub image-publishing configuration and comparing its registry settings with GHCR requirements. Done means the same container is published to GHCR as an additional pullable mirror; no file or test is identified in the issue.

Written by the indexing model from the issue text.