static get lockfileName() {
    return 'yarn.lock';
  }
Yarn packager.

Yarn specific packagerOptions (default):
  flat (false) - Use --flat with install
  ignoreScripts (false) - Do not execute scripts during install
  noNonInteractive (false) - Disable interactive mode when using Yarn 2 or above
  noFrozenLockfile (false) - Do not require an up-to-date yarn.lock
  networkConcurrency (8) - Specify number of concurrent network requests