Bug 1848125 - Expose Event and MessageEvent in AudioWorkletGlobalScope. r=webidl,smaug

It appears that it was in the spec all along, it's just something we missed on the Gecko side:
https://html.spec.whatwg.org/multipage/comms.html#the-messageevent-interface
https://dom.spec.whatwg.org/#interface-event

Differential Revision: https://phabricator.services.mozilla.com/D186434

dom/webidl/Event.webidl

@@ -10,7 +10,7 @@
  * liability, trademark and document use rules apply.
  */
 
-[Exposed=(Window,Worker), ProbablyShortLivingWrapper]
+[Exposed=(Window,Worker,AudioWorklet), ProbablyShortLivingWrapper]
 interface Event {
   constructor(DOMString type, optional EventInit eventInitDict = {});
 

dom/webidl/MessageEvent.webidl

@@ -7,7 +7,7 @@
  * https://html.spec.whatwg.org/#messageevent
  */
 
-[Exposed=(Window,Worker)]
+[Exposed=(Window,Worker,AudioWorklet)]
 interface MessageEvent : Event {
   constructor(DOMString type, optional MessageEventInit eventInitDict = {});