Add support for top horizontal scroll in MRT v3

[julSemeniuk]

Hi,
It would be very useful to have an option to render a horizontal scrollbar at the top of the table (in addition to the default bottom one).

Motivation: On wide + tall tables, reaching the bottom scrollbar is inconvenient. A top scrollbar improves navigation and usability for data-heavy use cases (analytics, finance, reporting)

Proposal: Add an optional prop (e.g. enableTopScroll /scrollbarPosition="top" | "bottom" | "both") to render a synchronized scrollbar at the top.

This small addition could make navigation much smoother without breaking changes.

Thanks for considering!