Issue Summary:

The expected function type for the externalGeocoder property in the MapboxGeocoder.GeocoderOptions interface is not accurate. The documentation states the expected function signature as:
(property) MapboxGeocoder.GeocoderOptions.externalGeocoder?: ((searchInput: string, features: GeoJSON.FeatureCollection<GeoJSON.Geometry>) => Promise<GeoJSON.FeatureCollection>) | undefined
This suggests that the function should return a Promise<GeoJSON.FeatureCollection>. However, in practice, the function is expected to return an Array<GeoJSON.Feature<GeoJSON.Geometry>> instead of a GeoJSON.FeatureCollection.

Actual Behavior:

When I write a function that returns a GeoJSON.FeatureCollection as described in the documentation, the Mapbox Geocoder doesn't work correctly. But if I modify the function to return an Array<GeoJSON.Feature<GeoJSON.Geometry>>, the Mapbox Geocoder works as expected.

Expected Behavior:

The documentation and type definition for the externalGeocoder property should be updated to reflect the correct expected return type, which is an Array<GeoJSON.Feature<GeoJSON.Geometry>> instead of a GeoJSON.FeatureCollection.

Proposed Resolution:

Update the type definition for the externalGeocoder property in the MapboxGeocoder.GeocoderOptions interface to the following:
(property) MapboxGeocoder.GeocoderOptions.externalGeocoder?: ((searchInput: string, features: GeoJSON.FeatureCollection<GeoJSON.Geometry>) => Promise<Array<GeoJSON.Feature<GeoJSON.Geometry>>>) | undefined
This will ensure the type definition accurately reflects the actual expected return type for the externalGeocoder function.