Add devShell to flake

flake.nix

@@ -17,6 +17,12 @@
             (super: self: { config-archive = super.callPackage ./lib/pkgs/config-archive.nix { }; })
           ];
       };
+
+      forAllSystems = function:
+        nixpkgs.lib.genAttrs [
+          "x86_64-linux"
+          "aarch64-darwin"
+        ] (system: function nixpkgs.legacyPackages.${system});
       
     in
       {
@@ -30,5 +36,11 @@
             ];
           };
         };
+
+        devShells = forAllSystems (pkgs: {
+          default = pkgs.mkShell {
+            buildInputs = [ pkgs.nixos-rebuild ];
+          };
+        });
       };
-}
+}