Built the experience system

We now have chests spawning in the map with different tiers that can give different amounts of experience:

Tier order (lowest to higher):

1. Wooden Chest (min: 1000exp / max: 2000exp)
2. Silver Chest (min: 2000exp / max: 5000exp)
3. Golden Chest (min: 5000exp / max: 10000exp)
4. Magic Chest (min: 10000exp / max: 17500exp)
5. Death Chest (min: 17500exp / max: 25000exp)

Unity Assets Chests Page