develop: Add Rust

flake.nix

@@ -123,5 +123,14 @@
         ];
       };
     };
+
+    devShells."${system}".default = let
+      pkgs = import nixpkgs { inherit system; };
+    in pkgs.mkShell {
+      packages = with pkgs; [
+        cargo
+        rustc
+      ];
+    };
   };
 }