add firefox extension template

externs/webextension_polyfill/urlbar/OnResultsRequestedEvent.hx

@@ -0,0 +1,19 @@
+package webextension_polyfill.urlbar;
+
+/**
+	When a query starts, this event is fired for the given provider if the provider is active for the query and there are no
+	other providers that are restricting. Its purpose is to request the provider's results for the query.
+	The listener should return a list of results in response.
+**/
+typedef OnResultsRequestedEvent = {
+	/**
+		Registers an event listener <em>callback</em> to an event.
+	**/
+	function addListener(callback:(query:Query) -> Array<Result>, providerName:String):Void;
+	/**
+		Deregisters an event listener <em>callback</em> from an event.
+	**/
+	function removeListener(callback:(query:Query) -> Array<Result>):Void;
+	function hasListener(callback:(query:Query) -> Array<Result>):Bool;
+	function hasListeners():Bool;
+};