Add submission # 7404

#7404

Author: ArduinoBot

registry.txt

@@ -8721,3 +8721,4 @@ https://github.com/Viderspace/Smooth-Axis-Arduino.git|Contributed|SmoothAxis
 https://github.com/nbulatovi/Quecduino.git|Contributed|Quecduino
 https://github.com/adafruit/Adafruit_SGP41.git|Recommended|Adafruit SGP41
 https://github.com/Alby312/AdvancedPID.git|Contributed|AdvancedPID
+https://github.com/raiotech-iot/RAIOT_MQTT.git|Contributed|RAIOT_MQTT