Update libraries.rst with ESP-NOW (#5322)

Fixes #2227

Author: devyte

doc/libraries.rst

@@ -164,6 +164,7 @@ Libraries that don't rely on low-level access to AVR registers should work well.
 -  `DimSwitch <https://github.com/krzychb/DimSwitch>`__ - Control electronic dimmable ballasts for fluorescent light tubes remotely as if using a wall switch.
 -  `Encoder <https://github.com/PaulStoffregen/Encoder>`__ - Arduino library for rotary encoders. Version 1.4 supports ESP8266.
 -  `esp8266\_mdns <https://github.com/mrdunk/esp8266_mdns>`__ - mDNS queries and responses on esp8266. Or to describe it another way: An mDNS Client or Bonjour Client library for the esp8266.
+-  `ESP-NOW <https://github.com/yoursunny/WifiEspNow>`__ - Wrapper lib for ESP-NOW (See `#2227 <https://github.com/esp8266/Arduino/issues/2227>`__)
 -  `ESPAsyncTCP <https://github.com/me-no-dev/ESPAsyncTCP>`__ - Asynchronous TCP Library for ESP8266 and ESP32/31B
 -  `ESPAsyncWebServer <https://github.com/me-no-dev/ESPAsyncWebServer>`__ - Asynchronous Web Server Library for ESP8266 and ESP32/31B
 -  `Homie for ESP8266 <https://github.com/marvinroger/homie-esp8266>`__ - Arduino framework for ESP8266 implementing Homie, an MQTT convention for the IoT.