repositories: update khoverlay URLs and description

[khumba]

Hello, I have moved khoverlay to Sourcehut and would like to update the URLs. Also the description was long out of date, this new one better reflects what is in the repository.

I would appreciate some confirmation the second, SSH source URL, ssh://git@git.sr.ht/~khumba/khoverlay. Should this be git+ssh:// instead? A quick search isn't showing any docs for what plus means here. I see that the few other overlays on Sourcehut all specify ssh://. Also, they all have a colon between git.sr.ht and the ~user, which is a copy-paste of what Sourcehut shows in their UI, but is probably wrong; I need to put a slash there instead for the URL to work, git clone doesn't like when I put a colon there:

git clone ssh://git@git.sr.ht/~khumba/khoverlay    # works
git clone ssh://git@git.sr.ht:~khumba/khoverlay    # doesn't

Thanks!