[V2] Provide explicit type values for the fields in the different area types

[MartinP460]

Description

It would be nice if the area objects in each of the maps were to include explicit values of all the fields. For example, the type of a region in the Region map should be:

type RegionType = {
  id: "syddanmark" | "sjaelland" // ...
  display_name: "Syddanmark" | "Hovedstaden" // ...
  // ...
}

instead of just a string for each of the properties. This would improve intellisense and mean that some equality checks would not throw a type error due to unknown properties.

Proposed solution

Casting the array of area data to const (using as const after the definition of the array) and using a generic to construct the correct type.