Add custom textures to Balloon Animals trades

[catter1]

Feature Request

The trades in the Wnadering Trader GUI for Balloon Animals should have a custom texture. Currently, the trade in the GUI is just a lead, with a custom name and lore for the mob type and its name, respectively.

With the resourcepack, the lead texture could be replaced with a sprite of the baby animal's head. Potentially could make it fancier by painting the face onto a balloon texture, or any other creative liberty.

Egg trades make sense to stay unchanged.

Example

Pretend that's a donkey face

[Bloo-dev]

Great idea! For textures I recommend we let a texture artist try their hand at it. Possibly @kyrkis, or maybe @TheSneakinSpider wants to give it a go.