Via this workflow we now can build and push our docker images to
the GitHub Docker container registry:
26a1ee4e61/.github/workflows/docker-build.yaml
GitHub does not charge for downloads to runners (hosted or self-hosted).
This can therefore save the project money if we download from GitHub's
Docker reigstry over Google Cloud's.
This is a test to ensure this works as intended.
Change-Id: Iccdb1b7a912f1e0a0d82b7f888694958099315b3