add new external flake to provide helper functions

flake.nix

@@ -8,6 +8,11 @@
 
     import-tree.url = "github:vic/import-tree";
 
+    helpers = {
+      url = "git+https://git.greyweather.dev/greyweather/nix-helper-flake";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+
     #nixpkgs-mesa-overlay.url = "github:nixos/nixpkgs/e4f9df8a27c2b4871c665368e65bdb6852dd93e6";
 
     home-manager = {