FIX: Make sure new user narrative returns toggleBookmark promise

* the call to this.super() was not returned so there is no promise
  to chain .then() with, causing errors for bookmarks with reminders

plugins/discourse-narrative-bot/assets/javascripts/initializers/new-user-narrative.js.es6

@@ -32,7 +32,7 @@ function initialize(api) {
           this.appEvents.trigger("post-stream:refresh", { id: this.id });
         });
       }
-      this._super();
+      return this._super();
     }
   });