Fixed: Restored robots.txt

(cherry picked from commit 37501094d7256e4dbe13de33b392933f6d475553)

frontend/gulp/build.js

@@ -10,7 +10,8 @@ gulp.task('build',
       'webpack',
       'copyHtml',
       'copyFonts',
-      'copyImages'
+      'copyImages',
+      'copyRobots'
     )
   )
 );