NPC / Slapper 2.7.1

Fixed unable to spawn some NPCs and delallcmd incorrect output

- Added support for offhand item
- Lots of bug fixes

Added new entities:
- Allay
- Axolotl
- Frog
- GlowSquid
- Tadpole
- Warden

> Human NPC: Improved compatibility with modern skins
> Made all NPCs immune to fire
> New NPC: Goat

> Improved NPC hitboxes
> New NPCs:
- Ravager
- Block:
* Use /npc edit <id> block <block id:meta> to change the block type

Fixed score tag saving for human entities & added piglin brute

Added new entities from 1.16

Fixed human NPC skins on 1.16

- Added new entities
- Added scoretag support for human NPCs
- Added %uuid placeholder for player UUID
- Added support for new skin properties
- Other fixes and performance improvements

Bug fixes