Add a drop item button.

[GraySloth]

Having played around with the 360 controler controls, I loved that you could press down on the d-pad to just drop items on the ground.

 

I want to make a mod that lets me middle mouse button click on a item in my inventory or being held by my mouse and drop it without having to place it somewhere, but I am having trouble finding a place to start with this one, can anyone help me out?