message: make url prop read only in Cesium3DTileset
diff: @@ -13,7 +13,6 @@ A Cesium3DTileset object will be attached to the PrimitiveCollection of the View
  */
  export interface Cesium3DTilesetCesiumProps {
  - url: Cesium.Resource | string | Promise<Cesium.Resource> | Promise<string>;
  show?: boolean;
  modelMatrix?: Cesium.Matrix4;
  shadows?: Cesium.ShadowMode;
  @@ -56,6 +55,7 @@ export interface Cesium3DTilesetCesiumProps {
  }
  export interface Cesium3DTilesetCesiumReadonlyProps {
  + url: Cesium.Resource | string | Promise<Cesium.Resource> | Promise<string>;
  pointCloudShading?: {
  attenuation?: boolean;
  geometricErrorScale?: number;
  @@ -90,7 +90,6 @@ export interface Cesium3DTilesetContext {
  }
  const cesiumProps: (keyof Cesium3DTilesetCesiumProps)[] = [
  - "url",
  "show",
  "modelMatrix",
  "shadows",
  @@ -129,7 +128,10 @@ const cesiumProps: (keyof Cesium3DTilesetCesiumProps)[] = [
  "specularEnvironmentMaps",
  ];
  -const cesiumReadonlyProps: (keyof Cesium3DTilesetCesiumReadonlyProps)[] = ["pointCloudShading"];
  +const cesiumReadonlyProps: (keyof Cesium3DTilesetCesiumReadonlyProps)[] = [
  + "url",
  + "pointCloudShading",
  +];
  const cesiumEventProps: EventkeyMap<any, keyof Cesium3DTilesetCesiumEvents> = {
  allTilesLoaded: "onAllTilesLoad",
  