Update repositories.txt (#5463)

Arduino library for SPI AD5231 and AD5235 10 bit digital potentiometers.

Author: RobTillaart

repositories.txt

@@ -5235,6 +5235,7 @@ https://github.com/RobTillaart/ACD3100
 https://github.com/RobTillaart/ACS712
 https://github.com/RobTillaart/AD5144A
 https://github.com/RobTillaart/AD520X
+https://github.com/RobTillaart/AD523X
 https://github.com/RobTillaart/AD5245
 https://github.com/RobTillaart/AD5246
 https://github.com/RobTillaart/AD5248