LibWeb: Implement MediaQueryList.onchange

Author: https://github.com/Lubrsi
Commit: 46686f7f94
Pull-request: https://github.com/SerenityOS/serenity/pull/10288
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/CSS/MediaQueryList.h

@@ -44,6 +44,9 @@ public:
     void add_listener(RefPtr<DOM::EventListener> listener);
     void remove_listener(RefPtr<DOM::EventListener> listener);
 
+    void set_onchange(HTML::EventHandler);
+    HTML::EventHandler onchange();
+
 private:
     MediaQueryList(DOM::Document&, String);