feat: support author-provided prev/next controls

[DannyJoris]

This change allows a user to optionally provide their own HTML wrappers and Tabled recognizes them when present. You can provide the following and Tabled will pick these elements up, binding the click events to the buttons.

<div class="tabled">
  <div class="tabled__navigation">
    <button type="button" class="tabled__previous" aria-label="Previous column">Previous</button>
    <button type="button" class="tabled__next" aria-label="Next column">Next</button>
  </div>
  <table>
    ...
  </table>
</div>

Inspired by Splide: https://splidejs.com/guides/arrows/#custom-arrows