Automatically build and upload Docker containers

Problem

Sometimes, we will need to rebuild the Docker images that are hosted on Docker Hub, e.g., when external versions change. This is currently done manually.

Solution

Have a GitHub workflow that automatically runs the Dockerfiles and uploads the images to Docker hub when triggered. This doesn't need to happen with every pull request since it's unnecessary and resource-consuming. Rather, the action would need to figure out for itself when it's necessary to trigger a rebuild.

4C has an action to check if a Docker rebuild is required. I think they do that by comparing the hashes of their dependencies.

Additional context

See the discussion in #308.

Code of Conduct

• I agree to follow this project's Code of Conduct and Contributing Guidelines

Start with the Dockerfiles in the Docker directory and the discussion in #308, then review the linked 4C GitHub actions for dependency-hash checking. Define the workflow's rebuild trigger and Docker Hub upload steps around those inputs. Done means a triggered workflow detects when rebuilding is needed, builds the images, and uploads them successfully.