Docs: Include `properties` in FeatureCollection example

[Johngeorgesample]

I tried copy/pasting the example for Native Mapbox Layers, but encountered a TypeScript error.

[tsserver 2741] [E] Property 'properties' is missing in type '{ type: "Feature"; geometry: { type: "Point"; coordinates: number[]; }; }' but required in type 'Feature<Geometry, GeoJsonProperties>'.

This PR addresses that error by adding properties to the object.