add $selfillum support for "Eyes" vertex shader

[TotallyARussian]

not sure how possible this is, but i'd like support for the $selfillum parameter for the "Eyes" vertex shader to allow for glowing eyes, i've searched the whole internet and haven't found anything that would let me achieve that effect without having to use another shader, which would mean losing eye movement, i'm not sure about the "EyeRefract" shader as i haven't used it cause it's way more complicated than the og "Eyes" shader, but i don't think it allows for glowing textures either.