Using the same ResizeObserver instance for all hooks for better performance

[DanielGiljam]

Have you considered using the same ResizeObserver for all hooks instead of creating a separate ResizeObserver instance for each hook? Multiple observers each observing one element seems to be less performant than one observer observing multiple elements (see WICG/resize-observer#59 (comment)).

[ZeeCoder]

Yes, feel free to chip in this discussion:
#80