Add submission # 5716

#5716

Author: ArduinoBot

registry.txt

@@ -7768,3 +7768,4 @@ https://github.com/schreibfaul1/ESP32-audioI2S.git|Contributed|ESP32-audioI2S-ma
 https://github.com/median-dispersion/XPT2046-Driver.git|Contributed|XPT2046 Driver
 https://github.com/stacknix/stackmq-esp32.git|Contributed|Stackmq
 https://github.com/scottyob/IgcLogger.git|Contributed|IgcLogger
+https://github.com/marekburiak/ESP32_MQTTClient.git|Contributed|ESP32_MQTTClient