Update repositories.txt (#6502)

Arduino library for the TCRT5000 reflective optical sensor (IR).

Author: RobTillaart

repositories.txt

@@ -5787,6 +5787,7 @@ https://github.com/RobTillaart/SWSPI
 https://github.com/RobTillaart/TCA9548
 https://github.com/RobTillaart/TCA9554
 https://github.com/RobTillaart/TCA9555
+https://github.com/RobTillaart/TCRT5000
 https://github.com/RobTillaart/TCS3210
 https://github.com/RobTillaart/Temperature
 https://github.com/RobTillaart/TEMT6000