LibWeb/HTML: Port Window.structuredClone() to IDL

Author: https://github.com/linusg
Commit: 129ab02470
Pull-request: https://github.com/SerenityOS/serenity/pull/17752
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/HTML/MessagePort.idl

@@ -4,12 +4,15 @@
 // https://html.spec.whatwg.org/multipage/web-messaging.html#messageport
 [Exposed=(Window,Worker,AudioWorklet), Transferable]
 interface MessagePort : EventTarget {
-
     undefined postMessage(any message);
     undefined start();
     undefined close();
 
+    // event handlers
     attribute EventHandler onmessage;
     attribute EventHandler onmessageerror;
-
+};
+
+dictionary StructuredSerializeOptions {
+    sequence<object> transfer = [];
 };