geoJsonIconUrls

The distinct icon images a GeoJSON document asks for.

The renderer has to know these before it composes: MapLibre picks an icon per feature from a case over the values it was given, and there is no way to register an image under a name chosen later — ImageManager's acquire methods are internal to the library. So the document is read once, here, rather than left to the map to discover.

Returns nothing for a document that will not parse. An import that cannot be read is already drawing nothing; the renderer falling back to plain points is the better failure than no layer at all.