[Koi](https://github.com/baduhai/Koi) is a scheduling theme switcher for
KDE that I have been using on Plasma 6 for the last few days. It has
been working great for me, and I was originally looking for it within
`nixpkgs`, but couldn't find it, so here it is.
This is the derivation I have been testing it with:
7edb3f60a8
I have also been running it from my own development fork of `nixpkgs`
using the same code I'm submitting here.
ca3c9deb90