Howto: "kinda" declaratively install extensions for ungoogled-chromium

Extensions installed into chromium using the os config carry over to ungoogled-chromium.
This makes it possible to install extensions for ungoogled chromium without having to download them manually.

First add extensions to chromium like this:

environment.systemPackages = with pkgs; [ chromium ];
programs.chromium = {
  enable = true;
  extensions = [ "cjpalhdlnbpafiamejdnhcphjbkeiagm" # ublock origin ];
};

Run nixos-rebuild switch.
Change the chromium package to ungoogled chromium and rebuild again:

environment.systemPackages = with pkgs; [ ungoogled-chromium ];

This could probably be improved upon…