Update repositories.txt (#7044)

Submit SerialCommandManager

Author: k3ldar

repositories.txt

@@ -8261,6 +8261,7 @@ https://github.com/Faizyee/Socketyee
 https://github.com/ivanmari/bare-poller
 https://github.com/lahavg/QMI8658-Arduino-Library
 https://github.com/k3ldar/MovementDetector
+https://github.com/k3ldar/SerialCommandManager
 https://github.com/marcel-naderer/Lexo
 https://github.com/joshua-8/xrp-style-wpilib-comms
 https://github.com/bitbank2/bb_imu