MakerGear M3 Robust Filament Guide

Replaces the thin filament guide for the MakerGear M3 printer. Unlike the stock version, this will securely hold the guide tube vertical, so that the filament will not bend or snag on the edge of the guide hole. I made it with some extra structural support to ensure it can withstand the torque from a stiffer PTFE tube, as the stock plastic tube was giving me under-extrusion due to friction. Only tested on an M3 but should fit on an M2 as well.