describe LDevice

As a user of `scl-diff` I would like to have the SCL element `LDevice` description.

** Requirements **
- return a `LDevice`

```ts
export LDeviceDescription extends NamingDescription {
   /** LDevice attribute ldName */
   ldName?: string
   /** LDevice child LN0 */
   ln0: LN0Description;
   /** LDevice children LN */
}
```
