Update repositories.txt (#5752)

Add https://github.com/RobTillaart/TCS3210 color to frequency convertor

Author: RobTillaart

repositories.txt

@@ -5567,6 +5567,7 @@ https://github.com/RobTillaart/SWSPI
 https://github.com/RobTillaart/TCA9548
 https://github.com/RobTillaart/TCA9554
 https://github.com/RobTillaart/TCA9555
+https://github.com/RobTillaart/TCS3210
 https://github.com/RobTillaart/Temperature
 https://github.com/RobTillaart/TEMT6000
 https://github.com/RobTillaart/timing