arscode 0.1.0

Working with the German Amtlicher Regionalschlüssel (ARS): parse, validate and manipulate ARS codes.
Documentation
# arscode

`arscode` provides Rust types and utilities for working with the German
`Amtlicher Regionalschlüssel (ARS)` — a twelve-digit hierarchical regional
classification used to identify administrative regions in Germany from the
country level down to municipalities.

Features
- Parse and format ARS codes
- Validate ARS code parts (state, district, county, admin associations, municipality)
- Inspect and navigate administrative hierarchy (parent/child levels)
- Convert between `FederalState` and `ARSCode`

Examples
```
use arscode::{ARSCode, ARSLevel, FederalState};

let municipality = ARSCode::new(5, 3, 15, 8, 4, 42).unwrap();
assert_eq!(municipality.level(), ARSLevel::MUNICIPALITY);
println!("{}", municipality);

let state: ARSCode = FederalState::Hamburg.into();
assert_eq!(state.level(), ARSLevel::STATE);
```

Reference
- Wikipedia (DE): Amtlicher Gemeindeschlüssel — Regionalschlüssel
  <https://de.wikipedia.org/wiki/Amtlicher_Gemeindeschl%C3%BCssel#Regionalschl%C3%BCssel>

License
This project is licensed under the MIT License - see the `LICENSE` file for details.