Add demo to documentation

[JasPanesar]

If there's a quick way to contribute this I'm happy to do so, it would be great to have a working demo right on the documentation site.

[batistafrancis]

I'd like to use this to schedule and unschedule something every 10 minutes, but I did not find it in doc.
So.. I suggest you to add a real example in the docs.

const Scheduler = () => {

    // returns true if there’s room to schedule at ‘time’
    const couldScheduleAt = (time) => {}

    // returns true if we successfully scheduled
    const scheduleAt = (time) => {}

    // Choose an available time to schedule at, and return that time
    const schedule = () => {}

    // returns true if we successfully unscheduled something
    const unScheduleAt = (time) => {}
}