Update repositories.txt (#4002)

Arduino library for DS3232 RTC (minimalistic)

Author: RobTillaart

repositories.txt

@@ -4921,6 +4921,7 @@ https://github.com/RobTillaart/DS18B20_INT
 https://github.com/RobTillaart/DS2401
 https://github.com/RobTillaart/DS2438
 https://github.com/RobTillaart/DS28CM00
+https://github.com/RobTillaart/DS3232
 https://github.com/RobTillaart/ellipse
 https://github.com/RobTillaart/fast_math
 https://github.com/RobTillaart/FastMap