Create GitHub workflow for building images

[danisla]

After the selkies-gstreamer integration is done (#14), build a workflow to build all of the images and push them to GHCR with versions.

Follow the same build philosophy as the selkies-gstreamer repo:
https://github.com/selkies-project/selkies-gstreamer/tree/master/.github/workflows

Preserve the cloudbuild image building to allow folks to build and self-host images.

Strategy:

• master and dev branches are built when pushed to, images are tagged with the branch name respectively.
• Pushing a tag builds the images, creates a release and tags the images with latest