`options` are not optional in scheduleTask

[jgonera]

TypeScript typings don't allow me to invoke scheduleTask without options, I'm forced to pass an empty object:

  scheduleTask(
    // 12am UTC, everyday
    '0 0 * * *',
    () => {
      console.log('hello midnight');
    },
    {}, // <- can't skip this
  );