Exposed onprogress.

src/plugins/filetransfer.ts

@@ -178,11 +178,19 @@ export class Transfer {
     })
   }
 
+  /**
+   * Registers a listener that gets called whenever a new chunk of data is transferred.
+   * @param {function} Listener that takes a progress event.
+   */
+  onProgress(listener: (event: ProgressEvent) => any): void {
+    this.ft.onprocess = listener;
+  }
+
   /**
    * Aborts an in-progress transfer. The onerror callback is passed a FileTransferError
    * object which has an error code of FileTransferError.ABORT_ERR.
    */
-  abort() {
+  abort(): void {
      return this.ft.abort();
   }