Add end() API

NTPClient.cpp

@@ -128,6 +128,10 @@ String NTPClient::getFormattedTime() {
   return hoursStr + ":" + minuteStr + ":" + secondStr;
 }
 
+void NTPClient::end() {
+  this->_udp->stop();
+}
+
 void NTPClient::sendNTPPacket() {
   // set all bytes in the buffer to 0
   memset(this->_packetBuffer, 0, NTP_PACKET_SIZE);

NTPClient.h

@@ -67,4 +67,9 @@ class NTPClient {
      * @return time as raw seconds
      */
     unsigned long getRawTime();
+
+    /**
+     * Stops the underlying UDP client
+     */
+    void end();
 };

keywords.txt

@@ -9,6 +9,7 @@ NTPClient         KEYWORD1
 #######################################
 
 begin             KEYWORD2
+end               KEYWORD2
 update            KEYWORD2
 forceUpdate       KEYWORD2
 getDay            KEYWORD2