Implement missing features into the Level crate

[akashic-records-of-the-abyss]

The level API i developed doesnt have all features yet sadly. It still needs

• Biomes (Implement missing level features: Biomes #108)
• Entities (Implement missing level features: Entities #109)
• Players (Implement missing level features: Players #110)
• Hardcoded Spawning Areas
• Structures (Implement missing level features: Structures #111)
• Heightmaps
• Inventories (Implement missing level features: Inventories #112)

[theaddonn]

Please create seperate issues for each area and link them here.