FIX: Set text for titles in custom push notifications

This will fix a broken translation on the push notification
you receive when someone assigns you a topic.

config/locales/server.en.yml

@@ -4342,6 +4342,7 @@ en:
       linked: '%{username} linked to your post from "%{topic}" - %{site_title}'
       confirm_title: "Notifications enabled - %{site_title}"
       confirm_body: "Success! Notifications have been enabled."
+      custom: "Notification from %{site_title}"
 
   staff_action_logs:
     not_found: "not found"