Add "Peeking" Shulker heads

[EvModder]

Shulkers have 3 states: Closed, Peeking, and Open.
Currently we only have textures for Closed and Open states.
Perhaps look into working with Nano Team or commissioning on minecraft-heads for these missing textures.

[machinesmith42]

I will work on it at some point.

[machinesmith42]

Also what does the peeking one look like