Add new repository link for rtc (#7392)

Add rtc - simple funtions with doc

Author: Pandiyarajk

repositories.txt

@@ -8712,6 +8712,7 @@ https://github.com/hidori/DigitalButton
 https://github.com/PaulNTU/PandaCam
 https://github.com/hidori/ProgMemFS
 https://github.com/joy-it/JoyIT_LSM6DS3TR-C
+https://github.com/Pandiyarajk/rtc
 https://github.com/steambinhlong/SBLC
 https://github.com/MR01Right/BH1730FVC
 https://github.com/romoloman/esp32-rmt-pwm-reader