Access river geometry from Nominatim API

[fnattino]

Instead of retrieving the river centerline from the Overpass API searching for all the waterway: in a bbox, we could query the Nominatim API and use the OSM ID to retrieve the specific feature.

See current implementatio in the CRiSpApp: https://github.com/CityRiverSpaces/CRiSpApp/blob/prototype/app/app.R