message: expose GroundPrimitive and GroundPrimitiveCollection
diff: @@ -26,6 +26,8 @@ export { default as EntityDescription } from "./EntityDescription";
  export { default as Fog } from "./Fog";
  export { default as GeoJsonDataSource } from "./GeoJsonDataSource";
  export { default as Globe } from "./Globe";
  +export { default as GroundPrimitive } from "./GroundPrimitive";
  +export { default as GroundPrimitiveCollection } from "./GroundPrimitiveCollection";
  export { default as ImageryLayer } from "./ImageryLayer";
  export { default as ImageryLayerCollection } from "./ImageryLayerCollection";
  export { default as KmlDataSource } from "./KmlDataSource";
  