New Items Added

[loportol]

Related to #27

This creates three new items: poison, and two alternative health items, fish food and pellets.

Item description:
Poison

• Interactable Item that drains a player's health to zero
  Fish food
• Intractable item that provides 50 percent of the maximum health back, caps at maximum health
  Pellets
• Intractable item that provides 25 percent of the maximum health back, caps at maximum health

All pngs were created by me and are meant to just be sample fill ins.

[odecay]

Whats going on with the duplicated files in this PR? Is there a way we can remove the items inside the box folder and have them be linked by path instead?

[odecay]

bors merge

[odecay]

Moved stuff around a bit, Items all working as intended, thank you for your contribution @loportol

[bors]

Build succeeded:

• Check Rust formatting
• Clippy correctness checks (wasm32-unknown-unknown, web-target)
• Clippy correctness checks (x86_64-unknown-linux-gnu, target)