Update libraries.md

Author: probonopd

doc/libraries.md

@@ -143,6 +143,7 @@ Libraries that don't rely on low-level access to AVR registers should work well.
 - [DallasTemperature](https://github.com/milesburton/Arduino-Temperature-Control-Library.git)
 - [DHT-sensor-library](https://github.com/adafruit/DHT-sensor-library) - Arduino library for the DHT11/DHT22 temperature and humidity sensors. Download latest v1.1.1 library and no changes are necessary.  Older versions should initialize DHT as follows: `DHT dht(DHTPIN, DHTTYPE, 15)`
 - [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.
 - [NeoPixel](https://github.com/adafruit/Adafruit_NeoPixel) - Adafruit's NeoPixel library, now with support for the ESP8266 (use version 1.0.2 or higher from Arduino's library manager).
 - [NeoPixelBus](https://github.com/Makuna/NeoPixelBus) - Arduino NeoPixel library compatible with ESP8266. Use the "DmaDriven" or "UartDriven" branches for ESP8266. Includes HSL color support and more.
 - [PubSubClient](https://github.com/Imroy/pubsubclient) - MQTT library by @Imroy.