Keep websocket connection alive

tfw/components/terminal/terminado_mini_server.py

@@ -17,7 +17,7 @@ class TerminadoMiniServer:
             url,
             TerminadoMiniServer.ResetterTermSocket,
             {'term_manager': self._term_manager}
-        )])
+        )], websocket_ping_interval=30)
 
     @property
     def term_manager(self):

tfw/main/tfw_server.py

@@ -28,7 +28,7 @@ class TFWServer:
             r'/ws', ZMQWebSocketRouter, {
                 'listener': self._listener,
             }
-        )])
+        )], websocket_ping_interval=30)
 
     def listen(self):
         self.application.listen(TFWENV.WEB_PORT)