Improve macOS/iOS/Web thread safety

Co-authored-by: daxpedda <daxpedda@gmail.com>

src/platform_impl/linux/mod.rs

@@ -306,6 +306,14 @@ impl Window {
         }
     }
 
+    pub(crate) fn maybe_queue_on_main(&self, f: impl FnOnce(&Self) + Send + 'static) {
+        f(self)
+    }
+
+    pub(crate) fn maybe_wait_on_main<R: Send>(&self, f: impl FnOnce(&Self) -> R + Send) -> R {
+        f(self)
+    }
+
     #[inline]
     pub fn id(&self) -> WindowId {
         match self {