LibWeb: Start implementing the MediaQueryList interface

Author: https://github.com/linusg
Commit: 4155cc7ed5
Pull-request: https://github.com/SerenityOS/serenity/pull/10002

Userland/Libraries/LibWeb/CSS/MediaQueryList.idl

@@ -0,0 +1,9 @@
+[Exposed=Window]
+interface MediaQueryList : EventTarget {
+    readonly attribute CSSOMString media;
+    readonly attribute boolean matches;
+    // TODO:
+    // undefined addListener(EventListener? callback);
+    // undefined removeListener(EventListener? callback);
+    // attribute EventHandler onchange;
+};