Add submission # 3721

#3721

Author: ArduinoBot

registry.txt

@@ -6566,3 +6566,4 @@ https://github.com/s-light/slight_mapping.git|Contributed|slight_mapping
 https://github.com/s-light/slight_easing.git|Contributed|slight_easing
 https://github.com/NicolasNewman/ArgParse.git|Contributed|ArgParse
 https://github.com/alireza7575/MKS_SERVO57.git|Contributed|MKS_SERVO57
+https://github.com/sparkfun/SparkFun_Toolkit.git|Contributed|SparkFun Toolkit