Draft: Resolve "Examples: add an example with geolocalized images"

This MR adds the geolocalized_images that reads features from a geojson file, then display it using a FeatureCollection. Clicking on a feature then displays a card, with an image and a description from Wikipedia:

Closes #120

TODO

• Make the elevation callback work for all geometries (and not only polygons)
• Make it possible to display the features at all levels in FeatureCollection
• Dynamically update geometries that are draped on the terrain when new elevation data is received