Add ref to X carriage part, once moved

[zruncho3d]

Currently here

https://github.com/zruncho3d/DuelingZero/blob/main/STLs/Low_Side_X_Carriage_x1.stl

[mjrider]

the carriage doesn't seem to be there anymore

[Otann]

the carriage doesn't seem to be there anymore

It's here now, but it seems it is for 0.1

https://github.com/zruncho3d/DuelingZero/blob/main/Archived_v1/STLs/Low_Side_X_Carriage_x1.stl