add inter quake model export support (.iqm)

[notester32-ui]

can add inter quake model support to export?, useful for raylib 3D proyects and quake fangames

the files https://github.com/lsalzman/iqm

[JannisX11]

A bit too niche for Blockbench itself, I'll add it as a plugin idea.

[notester32-ui]

great :3