add translatable description

chatstate/chatstate.py

@@ -15,6 +15,10 @@ class ChatstatePlugin(GajimPlugin):
 
     @log_calls('ChatstatePlugin')
     def init(self):
+        self.description = _('Chat State Notifications in roster.'
+'Font color of the contact varies depending on the chat state.\n'
+'The plugin does not work if you use custom font color for contacts in roster.\n'
+'http://trac.gajim.org/ticket/3628.\nhttp://xmpp.org/extensions/xep-0085.html')
         self.config_dialog = None  # ChatstatePluginConfigDialog(self)
         self.events_handlers = {'chatstate-received':
                                     (ged.GUI2, self.chatstate_received), }