Add suport for EyeRefract shaders

[Xephobia]

That would be so cool since now every carachter eyes use this shader. The parameter would be $iris ; $corneatexture

[Xephobia]

I found a temporary way to do it : for the $iris parameter, place the texture in the base color node

[Xephobia]

also for now don't load the alpha, in the valve documentation, they say it's for controlling the noisiness of the cornea but i don't know how to implement the cornea yet