Add libhandy to nix shell

shell.nix

@@ -1,12 +1,32 @@
-{ pkgs ? import <nixpkgs> {} }: with pkgs;
+let
+  pkgs = import <nixpkgs> {
+    overlays = [
+      (
+        self: super: {
+          libhandy = super.libhandy.overrideAttrs (
+            old: {
+              src = pkgs.fetchFromGitLab {
+                domain = "gitlab.gnome.org";
+                owner = "BenjaminSchaaf";
+                repo = "libhandy";
+                rev = "14431ed38cd0d655678497310a6400c7ee5ce68f";
+                sha256 = "1528m91h5pllacalmih7fy3gf7f3s1kq0n3kix1gc1q43wkbjq91";
+              };
+            }
+          );
+        }
+      )
+    ];
+  };
+in
 pkgs.mkShell {
-  nativeBuildInputs = [
+  nativeBuildInputs = with pkgs; [
     gobject-introspection
     python3Packages.setuptools
     wrapGAppsHook
   ];
 
-  buildInputs = [
+  buildInputs = with pkgs; [
     bashInteractive
     flatpak
     flatpak-builder
@@ -15,6 +35,7 @@ pkgs.mkShell {
     glib
     gobjectIntrospection
     gtk3
+    libhandy
     libnotify
     pango
     pkgconfig