LibWeb: Add the missing CloseEvent IDL constructor

Author: https://github.com/IdanHo
Commit: ded8e84f32
Pull-request: https://github.com/SerenityOS/serenity/pull/10299

Userland/Libraries/LibWeb/HTML/CloseEvent.idl

@@ -1,7 +1,15 @@
+#import <DOM/Event.idl>
+
 interface CloseEvent : Event {
+    constructor(DOMString type, optional CloseEventInit eventInitDict = {});
 
     readonly attribute boolean wasClean;
     readonly attribute unsigned short code;
     readonly attribute USVString reason;
-
+};
+
+dictionary CloseEventInit : EventInit {
+    boolean wasClean = false;
+    unsigned short code = 0;
+    USVString reason = "";
 };