Server Backpacks!

Changelog

• Added a backpack block:
  • You can now place backpacks.

• Added 3 new configuration entries for customizing backpack's position when equipped in the Trinkets back slot:
  • back_positions: Adjusts the backpack’s position on the player’s back.
  • back_yaw: Controls horizontal rotation (left/right) of the backpack.
  • back_pitch_when_sneaking: Alters the tilt angle of the backpack when the player is sneaking.

• Added /backpacks command:
  • /backpacks list: Lists created backpack instances.
  • /backpacks open <UUID>: Specify an UUID to open a backpack instance.

• Added /open command:
  • /open: Allows to open a backapck when it is equipped on the trinkets back slot.