nixos-generate-config: Use the Firefox module (#287614)

      #   isNormalUser = true;

      #   extraGroups = [ "wheel" ]; # Enable ‘sudo’ for the user.

      #   packages = with pkgs; [

      #     firefox

      #     tree

      #   ];

      # };

      # programs.firefox.enable = true;

      # List packages installed in system profile. To search, run:

      # \$ nix search wget

      # environment.systemPackages = with pkgs; [