ESP8266WiFi library documentation (#2388)

* New section with ESP8266WiFi library documentation

* ESP8266WiFi library documentation

1. Introduction - example, diagnostic, doxygen
2. Station - examples, new doc
3. Soft Access Point - examples, new doc
4. Scan - examples, new doc
5. Client - examples, ref. Arduino, setNoDelay, list of functions
6. Client Secure - examples, loadCertificate, setCertificate, list of
functions
7. Server- examples, ref. Arduino, setNoDelay, list of functions
8. UDP - examples, ref. Arduino, Multicast UDP
9. Generic - examples, onEvent, WiFiEventHandler, persistent, mode, list
of functions

* Fixed numbered list

doc/esp8266wifi/client-class.md

@@ -0,0 +1,65 @@
+---
+title: ESP8266WiFi Client Class
+---
+
+[ESP8266WiFi Library :back:](readme.md#client)
+
+
+## Client Class
+
+Methods documented for [Client](https://www.arduino.cc/en/Reference/WiFiClientConstructor) in [Arduino](https://github.com/arduino/Arduino)
+
+1.  [WiFiClient()](https://www.arduino.cc/en/Reference/WiFiClient)
+2.  [connected()](https://www.arduino.cc/en/Reference/WiFiClientConnected)
+3.  [connect()](https://www.arduino.cc/en/Reference/WiFiClientConnect)
+4.  [write()](https://www.arduino.cc/en/Reference/WiFiClientWrite)
+5.  [print()](https://www.arduino.cc/en/Reference/WiFiClientPrint)
+6.  [println()](https://www.arduino.cc/en/Reference/WiFiClientPrintln)
+7.  [available()](https://www.arduino.cc/en/Reference/WiFiClientAvailable)
+8.  [read()](https://www.arduino.cc/en/Reference/WiFiClientRead)
+9.  [flush()](https://www.arduino.cc/en/Reference/WiFiClientFlush)
+10.  [stop()](https://www.arduino.cc/en/Reference/WiFIClientStop)
+
+
+Methods and properties described further down are specific to ESP8266. They are not covered in [Arduino WiFi library](https://www.arduino.cc/en/Reference/WiFi) documentation. Before they are fully documented please refer to information below.
+
+
+### setNoDelay
+
+```cpp
+setNoDelay(nodelay)
+```
+
+With `nodelay` set to `true`, this function will to disable [Nagle algorithm](https://en.wikipedia.org/wiki/Nagle%27s_algorithm). 
+
+This algorithm is intended to reduce TCP/IP traffic of small packets sent over the network by combining a number of small outgoing messages, and sending them all at once. The downside of such approach is effectively delaying individual messages until a big enough packet is assembled.
+
+*Example:*
+```cpp
+clinet.setNoDelay(true);
+```
+
+
+### Other Function Calls
+
+```cpp
+uint8_t  status () 
+virtual size_t  write (const uint8_t *buf, size_t size) 
+size_t  write_P (PGM_P buf, size_t size) 
+size_t  write (Stream &stream) 
+size_t  write (Stream &stream, size_t unitSize) __attribute__((deprecated)) 
+virtual int  read (uint8_t *buf, size_t size) 
+virtual int  peek () 
+virtual size_t  peekBytes (uint8_t *buffer, size_t length) 
+size_t  peekBytes (char *buffer, size_t length) 
+virtual  operator bool () 
+IPAddress  remoteIP () 
+uint16_t  remotePort () 
+IPAddress  localIP () 
+uint16_t  localPort () 
+bool  getNoDelay () 
+```
+Documentation for the above functions is not yet prepared.
+
+
+For code samples please refer to separate section with [examples :arrow_right:](client-examples.md) dedicated specifically to the Client Class.