AsyncIdleComp - Create a IdleComp version that works with promises

[munizart]

IdleComp instances can handle any value very well:

IdleComp
  .of(5)
  .map(increment)
  .map(double)

Expect when it comes to Promises.

IdleComp
  .of(Promise.resolve(5))
  .map(increment) // NaN
  .map(double) // NaN

// Works, but only using idle time for scheduling promises micro-tasks
// that have higher precedence than macro-tasks (i.e user input) :(
IdleComp
  .of(Promise.resolve(5))
  .map(p => p.then(increment))
  .map(p => p.then(double))

We need a interface that can transform a chain into promise friendly, meaning that a AsynIdleComp will await until promises resolution and then schedule a idle computation.