如何在apple mapkit JS中添加覆盖完整地图的图层

<script src="https://cdn.apple-mapkit.com/mk/5.x.x/mapkit.js"></script>
<link rel="stylesheet" href="https://cdn.apple-mapkit.com/mk/5.x.x/mapkit.css">

<div id="map"></div>

let map = new mapkit.Map("map", {
  center: new mapkit.Coordinate(37.331827, -122.031151),
  showsMapTypeControl: true,
  showsZoomControl: true,
  showsUserLocation: true,
  zoomEnabled: true,
  region: new mapkit.CoordinateRegion(
    new mapkit.Coordinate(37.331827, -122.031151),
    new mapkit.CoordinateSpan(0.01, 0.01)
  )
});

let overlay = new mapkit.MapOverlay(map.region, {
  urlTemplate: "https://example.com/overlay/{x}/{y}/{z}.png"
});
map.addOverlay(overlay);