Introduce an OSAction that can be associated with menu items for mac platform compatibility.

Co-authored-by: Antonio <antonio@zed.dev>

crates/live_kit_client/examples/test_app.rs

@@ -20,6 +20,7 @@ fn main() {
             items: vec![MenuItem::Action {
                 name: "Quit",
                 action: Box::new(Quit),
+                os_action: None,
             }],
         }]);