[Tutorial] show using AbortController for simpler cleanup with event listeners about limber HOT 1 OPEN

  @action setupWindowListener() {
    /* setup */
    let cleanup = new AbortController();
    let { signal } = cleanup;
    window.addEventListener('beforeunload', this.handleUnload, { signal })

    /* tear down */
    registerDestructor(this, () => cleanup.abort);
  }

  @action setupWindowListener() {
    /* setup */
    let cleanup = new AbortController();
    window.addEventListener('beforeunload', this.handleUnload, cleanup)

    /* tear down */
    registerDestructor(this, () => cleanup.abort);
  }