Anycubic I3 Mega Prusa i3 X-Carriage Converter

This is a remix of petrzmax's great work: https://www.thingiverse.com/thing:2838383 which is based on the great design of Endlesshunt: https://www.thingiverse.com/thing:926794. I love this design because of its simplicity and the hassle-free belt holder.

I have inverted the belt holder position so there is no need to invert the X motor spin direction.

More changes:
- I could not find the step file for the belt holder so I have recreated it from scratch. Step file is now included. I also r