Add note in packing instructions about blinking after flashing

Author: maxwofford

docs/packaging/PACKING.md

@@ -88,8 +88,9 @@ The electronics box should contain:
 
 **Testing**
 
-To test the electonics, plug the steppers and servo into the main board, and try to run any of the art examples in the gallery.  [^1]
+To test the electonics, plug the steppers and servo into the main board, and try to run any of the art examples in the gallery.[^0][^1]
 
+[^0]: Your xiao rp2040 will flash 3 times on it's red LED if flashed.
 [^1]: If your xiao rp2040 isn't flashed, or acting strangly, use the flashing instructions provided in [the hardware instructions](../../hardware/motor-control-board/SETUP.md).
 
 The computer should connect properly to the board.