Ender 3 - Runout Sensor and Filament Guide Bracket

This bracket attaches to the extruder motor plate using the two screws which hold the lead nut in place, and does a couple of very important things:

Filament Guide
---------------------
A hole in the rear of the bracket is sized correctly for a 1/4-20 tap, which let me screw in a spare compression fitting from when I replaced my Bowden tube. This lets me use an arbitrarily long scrap of old tubing to guide the filament from the spool into the extruder assembly, with nice gentle bends and curves regardless of print height or spool placement. In fact, the spool no longer needs to be on top of the printer at all! If you keep yours on a detached holder, or in a dry box, or anywhere else, this tube will feed it right into the proper position nice and easy.

Runout Sensor Mount
---------------------
I'm using the filament sensor from TH3D, which mounts easily and securely using a couple of long 3mm bolts. I've gotten away with not using nuts (the threads are catching on an exposed