Create a Docker image to run locally GitHub actions
GlideinWMS includes in build/packaging/containers/gwms-ubuntu/ a Dockerfile that is made available in Docker Hub as glideinwms/gwms-ubuntu
Updating the Dockerfile in the master branch automatically updates the image (previo build times on hub.docker).
The current image is incomplete and not tested.
This image should allow to run locally GWMS GitHub actions (in .github/) using act and glideinwms/gwms-ubuntu as runner image (-P option)