flutter_desktop: get double click time, win

Signed-off-by: fufesou <shuanglongchen@yeah.net>

src/platform/macos.rs

@@ -537,3 +537,9 @@ pub fn quit_gui() {
         let () = msg_send!(NSApp(), terminate: nil);
     };
 }
+
+
+pub fn get_double_click_time() -> u32 {
+    // to-do: https://github.com/servo/core-foundation-rs/blob/786895643140fa0ee4f913d7b4aeb0c4626b2085/cocoa/src/appkit.rs#L2823
+    500 as _
+}