Add user and developer documentation

Create documentation for both users and developers:

- README updates:
  - Installation
  - CLI usage examples
  - Dependency notes
- CONTRIBUTING.md (optional for dev)
- docs/ directory or wiki for:
  - Metadata workflow
  - Map creation
  - Schema validation
- Add a sample Jupyter notebook showing:
  - Loading an OIM
  - Generating Aardvark metadata
  - Visualizing in Folium
