treewide: update which packages I'm currently maintaining

Idea shamelessly stolen from 4e60b0ef.

I realized that I don't really know anymore where I'm listed as maintainer and what
I'm actually (co)-maintaining which means that I can't proactively take
care of packages I officially maintain.

As I don't have the time, energy and motivation to take care of stuff I
was interested in 1 or 2 years ago (or packaged for someone else in the
past), I decided that I make this explicit by removing myself from several
packages and adding myself in some other stuff I'm now interested in.

I've seen it several times now that people remove themselves from a
package without removing the package if it's unmaintained after that
which is why I figured that it's fine in my case as the affected pkgs
are rather low-prio and were pretty easy to maintain.