* use `flushSync` instead of `d.nextFrame`
This guarantees that after the `flushSync` call the DOM is updated. This
means that we don't have to guess and delay by a double
`requestAnimationFrame` (`nextFrame`) and _hope_ that the DOM was
updated already.
* inline disposables call
Each function in the `disposables()` object returns a cleanup function
which means we can return this directly.
* inline if-statements
Small one, but consistent with `<Menu />` and `<Listbox />` components.
* inline `flushSync()` callbacks
Robin Malfait
2d3ec80314