Rhino configuration Y- endstop holder for FLSUN Cube

I really didn't like FLSUN placing the Y-Endstop on the frame and felt it made more sense to put it on the print-head itself.

I call this the "Rhino Y-Enstop" configuration - kinda' obvious why I think :)

This also works with the Chimira and Cyclops hotends because the headboard is the same for those.