Find a better solution for .i3/config & .i3/config.focus

[Utagai]

It is too hard to make sure these files stay in sync except for the parts where we want them to diverge. We should find a better way to keep these two in sync.

My guess is a simple templating solution combined with a commit hook is probably sufficient... that and/or a Github action to verify that the files are in sync could be a good solution.