[Suggestion] Add support for old skin textures

[randewd]

So, before Minecraft Version 1.8, player skins used 64x32 textures instead of 64x64 textures, but Blockbench doesn't have support for 64x32 textures for player models, and I was going to preview a old skin texture in Blockbench, because it's faster, but when I try to use the texture, it stretches out and looks weird. Screenshot below: