JJ Races NeoForge port

Original JJ Races concept, assets, and 1.12 accessory geometry:
Copyright the original JJ Races author, JdiJack.
Original project license: Apache License 2.0.

NeoForge 1.21.1 port and physical-size implementation prepared for private compatibility use.
Minecraft is a trademark of Microsoft. This project is not affiliated with Mojang or Microsoft.
