Test docker image building

Summary

The building of the Docker image is not tested. Hence any changes to the Dockerfile can only fail on branches that publish images.

Steps to reproduce

Commit to a branch on this project not matching /(^v[0-9]+\.[0-9]+\.[0-9]+$|^master$|^develop$)/ .

Proposed solution

Add an a CI test job for building the docker image (not submitting it to the registry)