message: docs: doc for asset option
diff: @@ -100,7 +100,13 @@ export interface LibraryOption extends DownloaderOption {
  * Change the host url of assets download
  */
  export interface AssetsOption extends DownloaderOption {
  + /**
  + * Swap customized assets download host.
  + */
  assetsHost?: string | string[];
  + /**
  + * Control how many assets download task should run at the same time.
  + */
  assetsDownloadConcurrency?: number;
  }
  /**
  