MK10 Extruder spring pre-tensioner

I was having issues with my extruder slipping on the filament and causing under-extrusion, which got even worse after I added an oiler to the filament. Instead of printing or buying a whole new adjustable extruder assembly, I decided to make a simple pre-tensioner to sit on top of the existing spring to tighten the grip on the filament. This may not be the perfect fix, but it was quick and it worked for me.

This adds 3mm of extra compression to the spring. If it needs to be shorter, just cut