add missing externs to repo

externs/webextension_polyfill/find/Static.hx

@@ -0,0 +1,16 @@
+package webextension_polyfill.find;
+
+typedef Static = {
+	/**
+		Search for text in document and store found ranges in array, in document order.
+	**/
+	function find(queryphrase:String, ?params:FindParamsType):js.lib.Promise<FindResult>;
+	/**
+		Highlight a range
+	**/
+	function highlightResults(?params:HighlightResultsParamsType):js.lib.Promise<ts.Undefined>;
+	/**
+		Remove all highlighting from previous searches.
+	**/
+	function removeHighlighting(?tabId:Float):js.lib.Promise<ts.Undefined>;
+};