Solidoodle MK4 fan mount for PEEK cooling

This is adapted from Lawsy's MK4 head for the Solidoodle, and provides a place to mount a 40mm fan to cool the PEEK. This is meant to help with a problem where you gradually build up a partial clog (that gets progressively worse) because too much heat is filtering up from the hot end into the PEEK, making the flow intermittent.

Actually I think it'd work on an MK3 as well. But not the MK5. I just haven't moved up to the MK5 yet.

NOTE that this is NOT intended to aim the fan at the print