Overworld: Document how to add and set up worlds and dungeons

[LeviUniAcc]

Requirement

Current Behavior

There is no documentation on how to adding and setting up worlds and dungeons, including minigame spots, NPCs and barriers, works.

Expected Behavior

There is documention provided.

DoD

• [x] Documentation is provided on how to add a world
• [x] Documentation is provided on how to add a dungeon
• [x] Documentation is provided on how to add and set up minigame spots
• [x] Documentation is provided on how to add and set up NPCs
• [x] Documentation is provided on how to add and set up barriers
• [x] Documentation is provided on how to add minimap icons