anycubic mega i3 better cooling

* Did some major updating:
1. duct points more down towards the bed. Without the silicone sock it would cool the extruder to the point where the heater couldn't keep up.
2. I removed un-necessary material above fan, leaving a hole to make it easier to plug in the fan
3. I added material inside so it goes from round to square improving airflow. I think the screw bosses were trapping flow.

As with most cheaper printers, the extruder cooling is not sufficient to give good surface finish. Tried to integrate a 5015 blower fan but the CFM was still low. Decided to go with a 60mm axial fan as the one I found pushes almost 30CFM. The fan mount will completely replace the existing outer metal cover. The heatsink fan will be re-used. You will need to buy a 60mm fan and re-use the existing connector (IE solder in the old connector).

https://www.amazon.com/gp/product/B07K2Y9XSH/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

You will also need Seven M3 x 10mm long SHCS, and fou