Texture Variants

[Inspirateur]

Proper support for texture variants needs to be done in the shader because of greedy meshing basically (see #19 (comment)). The shader needs to know the chunk position, the seed, get a buffer indicating texture variants (similar to animation offsets), and use these infos + UV mapping of the quads to give texture variants to individual blocks (giving it to individual quads would be weird for the player)

This is very low priority for now because it's not important and bothersome.