Prusa MK3 Indirect filament sensor mod for stock extruder

I created this interposer to allow mounting my indirect filament sensor mod to the stock extruder. This simple mod fixes the laser filament sensor so it will work with all filament colors, even clear. It does this by using a simple proxy (small bearing) that travels with the filament. The [laser sensor](https://os.mbed.com/components/PAT9125EL-Miniature-Optical-Navigation-f/) is actually designed to read stainless steel using its infrared laser, so this mod works reliably. I have been using