Update repositories.txt (#6541)

Author: mirosieber

repositories.txt

@@ -8038,6 +8038,7 @@ https://github.com/zamanturja/A9Gmod
 https://github.com/WBS-Wissen/Stepper8825Lib
 https://github.com/vladysor/SensEdu-Library
 https://github.com/mirosieber/Litime_BMS_ESP32
+https://github.com/mirosieber/OPT300x
 https://github.com/ByteVoltaTeam/PIDEasy
 https://github.com/styropyr0/BME688
 https://github.com/styropyr0/MPM10