Update repositories.txt (arduino#3132)

add CQRobotTDS, library for using a CQRobot TDS sensor

Author: redPanther

repositories.txt

@@ -4953,6 +4953,7 @@ https://github.com/razvan-mocanu/LC709204F
 https://github.com/red-scorp/LiquidCrystal_AIP31068
 https://github.com/red-scorp/SoftSPIB
 https://github.com/redkea/arduino-library
+https://github.com/redPanther/CQRobotTDS
 https://github.com/regimantas/Oversampling
 https://github.com/rei-vilo/PDLS_EXT3_Basic
 https://github.com/rei-vilo/PDLS_EXT3_Basic_Fast