Prusa i3 MK3S Spool Holder

An improved spool holder for the Prusa i3 MK3S that incorporates bearings and load cells into it, improving performance and information about how much filament is remaining.

I built a custom scale display for getting the values onto a small screen: [link](https://github.com/raveious/filament-scale)

The HX711 board that I used will fit nicely into the back PCB slot, while the protoboard I used (3cm x 7cm) fits into the front PCB slot. I might make a octoprint friendly version in the future,