Wait next frame on playin

[willybrauner]

Problem:

The parent component mount the component using a TransitionsManager instance :

const App = () => {
  const childIsMount = useIsMount(Child.transitionManager);
  return {childIsMount && <Child />}
}

The child can listen playStateSignal only on after being mounted with usePlayIn hook.

usePlayIn(Child.transitionsManager, async (done) => {
    // here, the "playStateSignal" handler content
    // this code is executed when the manager dispatch "play-in" state
  })

But sometimes the component start to listening after the TransitionManager instance dispatch "play-in" state. The child didn't catch this first dispatch and playIn is never fired.

This MR just Add a "next frame" hake in order to wait the child component will be rendered BEFORE the "play-in" state will be dispatched by the manager.