add template feature for domains and mailboxes

data/web/mailbox.php

@@ -40,6 +40,7 @@ $template_data = [
   'domains' => $domains,
   'mailboxes' => $mailboxes,
   'lang_mailbox' => json_encode($lang['mailbox']),
+  'lang_rl' => json_encode($lang['ratelimit']),
   'lang_datatables' => json_encode($lang['datatables']),
 ];