Add overlay to Layman registry

[EoD]

It would be great to have this overlay on Layman, so that people don't need to manually install it every time.

A short explanation on how to add it to the registry, while still hosting it on github can be found for example here:
https://blog.hartwork.org/?p=843
https://wiki.gentoo.org/wiki/Project:Overlays/User_Guide#How_to_get_more_involved

You basically create a bug report at bugs.gentoo.org and tell them the required information. If you have further questions, you might want to join the irc channels in the 2nd link.