LibWeb: Add oncontrollerchange to ServiceWorkerContainer

Author: https://github.com/ADKaster
Commit: 4df280689b
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/1293
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/HTML/ServiceWorkerContainer.idl

@@ -17,7 +17,7 @@ interface ServiceWorkerContainer : EventTarget {
     [FIXME] undefined startMessages();
 
     // events
-    [FIXME] attribute EventHandler oncontrollerchange;
+    attribute EventHandler oncontrollerchange;
     attribute EventHandler onmessage; // event.source of message events is ServiceWorker object
     attribute EventHandler onmessageerror;
 };