add jsdoc to indicate possibility to use getContent async

src/public/app/widgets/type_widgets/type_widget.js

@@ -39,7 +39,7 @@ export default class TypeWidget extends NoteContextAwareWidget {
     }
 
     /**
-     * FIXME: add async here to indicate promise?
+     * @returns {Promise|*} promise resolving content or directly the content
      */ 
     getContent() {}