Added Inventor file for AVR 8 Pin 20MHz 8K 4AD - ATtiny85

Added an Autodesk inventor file and stl file of the AVR 8 Pin 20MHz 8K
4AD - ATtiny85. As well as added the directory "AVR Microcontrollers". the only difference in the name that I had to remove is the "4AD" which is actually supposed to be "4A/D"