add firefox extension template

externs/webextension_polyfill/urlbar/Query.hx

@@ -0,0 +1,23 @@
+package webextension_polyfill.urlbar;
+
+/**
+	A query performed in the urlbar.
+**/
+typedef Query = {
+	/**
+		Whether the query's browser context is private.
+	**/
+	var isPrivate : Bool;
+	/**
+		The maximum number of results shown to the user.
+	**/
+	var maxResults : Float;
+	/**
+		The query's search string.
+	**/
+	var searchString : String;
+	/**
+		List of acceptable source types to return.
+	**/
+	var sources : Array<SourceType>;
+};