PRUSA Mk25 Laser Engraving Kit

Building off of some excellent work done by MARZSOLT on the Prusa Mk3:

https://www.instructables.com/id/Laser-Engraving-on-Your-Prusa-MK3/

I decided to modify it to fit the MK2.5 with he latest angled extruder fan. The key difference is that the Mk3 fan runs on 5Volts and the Mk2.5 on 12V, so I was able to use the fan voltage directly to drive this laser, no PCM required. Also incorporated a KEYSTONE RJ11 jack to easily toggle between laser and 3D printing using a little loopback dongle wh