add GH Action workflow to build and publish the Zoobot cuda docker image

[camallen]

Something like https://brendanthompson.com/posts/2022/02/using-github-actions-to-publish-container-images-to-azure-container-registry

Instead of manually rebuilding this rather large image on development machines we can use the GH Action compute time to do so.

I'll note that we do have to be careful with making sure we don't publish a broken image / execution env for zoobot, i.e. watch for upgrades to underlying packages etc that may deprecate relied on api / features and that's one of the reasons why i've held off on this and manually rebuilt the images myself after manual testing.