themefox manager — Legendofmiracles

A addon, for the themefox-manager application: https://github.com/alx365/Themefox-Manager.
It installs custom CSS themes for your firefox, from git and themefox URL's. (The themefox website is yet to be released). You have to have the themefox-manager desktop application installed, and setup (currently there is no way to do this yet, without diving into some stuff, since this is still in production)