Uses MvtPainter to display MVT geo tiles.
NOTE: Env var GLEAM_TILES_JSON_URL must be set at build time, to e.g. https://api.maptiler.com/tiles/v3/tiles.json?key=YOUR_API_KEY. ... If you don't have access to an MVT server but want to build this example anyway, you can set GLEAM_TILES_JSON_URL to anything (e.g. the empty string). The build will succeed but the example will throw errors at runtime.
