add tracking tag to .gitmodules for renovate to watch for new tags

I'm pretty sure that the way that !55 (merged) is supposed to work is that it is just watching the .gitmodules file for the url line, and looking for the comment marker (#) and whatever after that is captured as the currentVersion. That capture group is then managed by renovate's git-tags manager. That means it will look for the latest tags for the dependency (the cstate theme git repository) and if there is one newer that what is after # in .gitmodules it will propose a MR that will update that to the newest one.

I do not think it will actually update the submodule to that new tag, but it will alert you through a MR, that there is a new one, which is better than nothing.

The # is just a comment, I do not believe it is an actual indicator to git submodule that what follows is the tag that git-submodule should track.

However, to get this to work, you need to have the # marker, and the current tag you are at in the .gitmodules file, which is what this MR adds.