use SpecialRenderer in ItemRenderer

[jacobsjo]

This allows rendering chests and decorated pots as items

[misode]

Can the additionalMesh not be merged with the mesh returned from getDisplayMesh instead of passing it to the function?

const mesh = model.getDisplayMesh('gui', this.resources, tint)
mesh.merge(additionalMesh)

[jacobsjo]

The additionalMesh also need to get all the transformations that getDisplayMesh applies on the mesh, so it has to be merged before the transformations (or be transformed separately).

[misode]

I changed it so the ItemRenderer now transforms using the display setting separately, this way it can merge the special renderer mesh itself. I wondered whether I had to add back the deprecated method in BlockModel, but I don't mind a small breaking change for someone that is using this internal method.

Maybe this is not a problem, but when testing the demo (npm run demo) it seems like the special renderer texture mapping is slightly off. @jacobsjo do you have any idea why this is happening?

[jacobsjo]

That rewrite looks good, certainly much cleaner. The texture mapping in the demo was an issue with the UV of non-16x16 textures in the demo code itself.