Add esp8266/Arduino#3442 reference.

Author: beta-tank

README.md

@@ -4,4 +4,6 @@ Working demo project for [PlatformIO](https://platformio.org).
 
 It is using forked [PIO ESP8266 framework](https://github.com/beta-tank/platform-espressif8266) which targets *2.5.0-beta2* version of [Arduino framework](https://github.com/esp8266/Arduino.git#2.5.0-beta2).
 
+Based on [discussion](https://github.com/esp8266/Arduino/issues/3442)
+
 Before building and uploading set your credentials in `main.cpp` and set port in `platformio.ini`