feat: add onReady feature

[goooseman]

Adds a special --onReady flag.

Measure time not until the first render, but until onReady callback is not invoked from the component. Useful when you have something happening inside your component after the initial render. If enabled, a special onReady function is passed to the component as a prop, which can be called after the component has done all the initial tasks, for example:

// Your component

const FooComponent = ({ onReady }) => {
  useEffect(() => {
    doSomeHeavyCalculations().finally(() => onReady())
  }, [])
  return ()
}

[goooseman]

Tests are failing nevertheless they pass locally, will check tomorrow