Update repositories.txt (#6585)

UnexpectedMaker · web-flow · commit 16871bfc299a · 2025-07-13T10:45:23.000Z
Added Unexpected Maker Series[D] board helper library
diff --git a/repositories.txt b/repositories.txt
@@ -8210,3 +8210,4 @@ https://github.com/X-croot/L298N-XCR
 https://github.com/kkfranco98/FIR_Filters
 https://github.com/m-shintaro/SpresenseIMU
 https://github.com/msnicklous/CommandCatcher
+https://github.com/UnexpectedMaker/seriesd_arduino_helper
