Add Window::is_maximized method (#1804)

src/platform_impl/macos/window.rs

@@ -730,6 +730,11 @@ impl UnownedWindow {
         shared_state_lock.fullscreen.clone()
     }
 
+    #[inline]
+    pub fn is_maximized(&self) -> bool {
+        self.is_zoomed()
+    }
+
     #[inline]
     pub fn set_fullscreen(&self, fullscreen: Option<Fullscreen>) {
         trace!("Locked shared state in `set_fullscreen`");