Add connectionKeepAlive to keywords.txt and add comment for it

Author: sandeepmistry

HttpClient.h

@@ -48,6 +48,8 @@ class HttpClient : public Client
     HttpClient(Client& aClient, const String& aServerName, uint16_t aServerPort = kHttpPort);
     HttpClient(Client& aClient, const IPAddress& aServerAddress, uint16_t aServerPort = kHttpPort);
 
+    /** Enables connection keep-alive mode
+    */
     void connectionKeepAlive();
 
     /** Start a more complex request.

keywords.txt

@@ -28,6 +28,7 @@ endOfHeadersReached	KEYWORD2
 endOfBodyReached	KEYWORD2
 completed	KEYWORD2
 contentLength	KEYWORD2
+connectionKeepAlive	KEYWORD2
 headerAvailable	KEYWORD2
 readHeaderName	KEYWORD2
 readHeaderValue	KEYWORD2