modify firefox config, to use flake packages as extension

flake.nix

@@ -71,6 +71,23 @@
     in
     flake-parts.lib.mkFlake { inherit inputs; } {
       systems = flake-utils.lib.defaultSystems;
+      perSystem = (
+        { pkgs, system, ... }@args:
+        {
+          _module.args.pkgs = import inputs.nixpkgs {
+            inherit system;
+            config = {
+              allowUnfree = true;
+            };
+          };
+          packages = import ./pkgs (
+            args
+            // {
+              inherit inputs;
+            }
+          );
+        }
+      );
       flake =
         {
           nix.settings = {