Add information of HCI packet count mismatch error on readme

Author: asukiaaa

README.md

@@ -2,6 +2,22 @@
 
 A library to use xbox controller on ESP32.
 
+## Known issue.
+
+The following error occurs on ESP32.
+```
+lld_pdu_get_tx_flush_nb HCI packet count mismatch (1, 2)
+```
+
+It does not occur on ESP32C3 (may be also S3) because BLE5 may be needed to communicate with xbox controller.
+If you want to use this library without the error, please use ESP32 which supports BLE5.
+
+Related issues:
+- [Connection is not the first time](https://github.com/asukiaaa/arduino-XboxSeriesXControllerESP32/issues/3)
+- [BLE service discovery fails on low BLE connections](https://github.com/espressif/esp-idf/issues/8303)
+- [Request of some advice to solve lld_pdu_get_tx_flush_nb HCI packet count mismatch (1, 2)](https://github.com/h2zero/NimBLE-Arduino/issues/293)
+- [Reset scanning state without resetting esp32](https://github.com/h2zero/NimBLE-Arduino/issues/417)
+
 ## Update firmware of controller
 
 This libary is checked with firmware version `5.13.3143.0` for xbox series X controller.