Mendel90 square nozzle fanduct

This is a remix of the original Mendel90 x carriage fan.
It uses a square instead of a round nozzle hole for the hotend. This makes it less likely that the hotend will melt the fanduct, because the hotend's corners are further away from the plastic.

I also added some extra supports in the duct itself for better bridging the long distance in the duct. See last picture.

I have not printed this version, but do not expect any problems.
But I did print another variant of this fanduct, t