Function buildReachableRangeFeatures

buildReachableRangeFeatures(
    features: PolygonFeature[],
    labels: string[],
    theme?: GeometryTheme,
): PolygonFeature[]
Attaches labels and applies theme-specific geometry to reachable range polygon features.

Features must be ordered largest budget first (e.g. 30 min, 20 min, 10 min). For the inverted theme, polygons are converted to donuts and one extra innermost feature is appended.
Parameters
- features: PolygonFeature[]
  Polygon features from calculateReachableRange, ordered largest budget first.
- labels: string[]
  Label per feature in matching order (e.g. ['30 min', '20 min', '10 min']).
- theme: GeometryTheme = 'filled'
  Visual theme. Defaults to 'filled'.
Returns PolygonFeature[]
Example
```
const features = [range30min, range20min, range10min];
const labels   = ['30 min', '20 min', '10 min'];

module.show({
    type: 'FeatureCollection',
    features: buildReachableRangeFeatures(features, labels, 'inverted'),
});
```