Ender 3 (Pro, V2) filament sensor for dual gear extruder (now version 2)

No need for support, simple switch with roller and optional socket (wire could directly be soldered to switch). How to wire and stuff is showed in this guys video:

https://www.youtube.com/watch?v=2l7c3A6_eT4&list=PL4uOUQa48Sii1aqiq2XS3fQ5Gb0aNpIxP&index=8&t=200s

I built marlin for myself for my purpose, so it is not tested.

Version 1 have a few minor flaws:

• when pushing filament out, the filament sometimes comes out from the side
• bowden tube is not secure enough and this is the only place I am not reluctant to use simple couplers :D

Supports only needed for couple part :)