message: Add comment on the sentinel file setup
diff: @@ -2,6 +2,9 @@ import retry from 'async-retry';
  import fs from 'fs-extra';
  import progress from 'progress-stream';
  +// A sentinel file is created by a zip-unpack lambda within the Chromatic infrastructure once the
  +// uploaded zip is fully extracted. The contents of this file will consist of 'OK' if the process
  +// completed successfully and 'ERROR' if an error occurred.
  const SENTINEL_SUCCESS_VALUE = 'OK';
  export async function uploadZip(ctx, path, url, contentLength, onProgress) {
  