Fix documentation typo (esp8266#3240)

Author: Fohdeesha

doc/libraries.md

@@ -18,7 +18,7 @@ title: Libraries
 
 ## WiFi(ESP8266WiFi library)
 
-The [Wi-Fi library for ESP8266](https://github.com/esp8266/Arduino/tree/master/libraries/ESP8266WiFi) has been developed basing on [ESP8266 SDK](http://bbs.espressif.com/viewtopic.php?f=51&t=1023), using naming convention and overall functionality philosophy of [Arduino WiFi library](https://www.arduino.cc/en/Reference/WiFi). Over time the wealth Wi-Fi features ported from ESP9266 SDK to [esp8266 / Adruino](https://github.com/esp8266/Arduino) outgrow [Arduino WiFi library](https://www.arduino.cc/en/Reference/WiFi) and it became apparent that we need to provide separate documentation on what is new and extra.
+The [Wi-Fi library for ESP8266](https://github.com/esp8266/Arduino/tree/master/libraries/ESP8266WiFi) has been developed basing on [ESP8266 SDK](http://bbs.espressif.com/viewtopic.php?f=51&t=1023), using naming convention and overall functionality philosophy of [Arduino WiFi library](https://www.arduino.cc/en/Reference/WiFi). Over time the wealth Wi-Fi features ported from ESP9266 SDK to [esp8266 / Arduino](https://github.com/esp8266/Arduino) outgrow [Arduino WiFi library](https://www.arduino.cc/en/Reference/WiFi) and it became apparent that we need to provide separate documentation on what is new and extra.
 
 [ESP8266WiFi library documentation](esp8266wifi/readme.md) : [Quick Start](esp8266wifi/readme.md#quick-start) | [Who is Who](esp8266wifi/readme.md#who-is-who) | [Station](esp8266wifi/readme.md#station) | [Soft Access Point](esp8266wifi/readme.md#soft-access-point) | [Scan](esp8266wifi/readme.md#scan) | [Client](esp8266wifi/readme.md#client) | [Client Secure](esp8266wifi/readme.md#client-secure) | [Server](esp8266wifi/readme.md#server) | [UDP](esp8266wifi/readme.md#udp) | [Generic](esp8266wifi/readme.md#generic) | [Diagnostics](esp8266wifi/readme.md#diagnostics)