Add submission # 6967

#6967

Author: ArduinoBot

registry.txt

@@ -8413,3 +8413,4 @@ https://github.com/fulda1/SUSI2.git|Contributed|SUSI2
 https://github.com/Harmony-Maker-Club/AIP1640_LED_Matrix.git|Contributed|AIP1640_LED_Matrix
 https://github.com/MISTERNEGATIVE21/QuectelEC200U_CN.git|Contributed|QuectelEC200U_CN
 https://github.com/WeSpeakEnglish/ANTIRTOS_MODERN.git|Contributed|ANTIRTOS_MODERN
+https://github.com/hidori/MicroSerial.git|Contributed|MicroSerial