Some of us use addons. Some of us change the settings of addons. Some of us like to backup their saved changes, or manage them externally for example with nixos or home-manager.
For both, we want to manipulate the list of *changed* settings, and only those. Because during installation process in nixos/home-manager, or recovery from backup a new firefox profile is created from scratch. I want to have the possibility to only deal with the explicitly changed settings.
All settings, default and changed, live in the `addons.json`. I want this file to be broken up.
This could work similar to the `user.js`, which contains *changed* preferences, which then gets computed to the `prefs.js` containing *all* settings.