Update repositories.txt (#2476)

Author: nhz2

repositories.txt

@@ -2973,6 +2973,7 @@ https://github.com/newdigate/teensy-polyphony
 https://github.com/newdigate/teensy-audio-launch-ctrl
 https://github.com/NHBSystems/NHB_AD7794
 https://github.com/NHBSystems/NHB_AD7124
+https://github.com/nhz2/XYZgeomag
 https://github.com/niccokunzmann/UC121902-TNARX-A
 https://github.com/NicholasBerryman/GenericMotorDriver
 https://github.com/NicholasBerryman/USBControllerLib