Update repositories.txt (#6237)

Arduino15 · web-flow · commit 828d4b5fa419 · 2025-04-25T14:42:05.000Z
diff --git a/repositories.txt b/repositories.txt
@@ -7990,3 +7990,5 @@ https://github.com/TheKvc/ServoHack
 
 https://github.com/microbotsio/CodeCell-MicroLink
 https://github.com/eyr1n/RP2040PIO_CAN
+
+https://github.com/Arduino15/A15RGB
