Reworked enemies, and added pets as drops!

- Enemies are now all using better placeholder sprites instead of the previous squares.

- Enemies scale differently than before. Each type of enemy has a set of base stats, 5 points split between strength, vitality, and dexterity. Each stat gets multiplied by the enemy's level, and then a 5% variance is applied.

- Enemies will now properly face the direction of the player. If a player enters a stage from the left, all enemies will face left, and vice versa for the right side. If teleporting to a warpstone, the enemies on the left will face right, and the enemies on the right will face left.

-Enemies can now drop as pets. This also includes bosses! Pet drops scale similarly to item drops.

- Fixed a bug where coins were not decreasing immediately after purchasing an item from a shop.

- Fixed an issue with shop items displaying duplicate names, despite the items having different stats.