added watchdog feed

src/TinyGsmModem.tpp

@@ -203,6 +203,7 @@ class TinyGsmModem {
       if (check_signal) { thisModem().getSignalQuality(); }
       if (thisModem().isNetworkConnected()) { return true; }
       delay(250);
+      esp_task_wdt_reset();
     }
     return false;
   }