Add basic keyboard navigation tests

[nstepien]

No description provided.

[amanmahajan7]

Good tests 👍

[amanmahajan7]

👍 We also need to scroll to the selected cell in case is not visible. Consider a case

• Select a cell
• Scroll the grid so cell is not visible
• Focus on any element outside the grid
• Tab into the grid
• Grid only scrolls when the selected position is changed

May be we can do something like

const selectedPositionOnFocus = selectedPosition.idx === -1 ? { idx: 0, rowIdx: 0, mode: 'SELECT' } : { ...selectedPosition };
if (isCellWithinBounds(selectedPositionOnFocus)) {
    setSelectedPosition(selectedPositionOnFocus);
}

Wdyt?

[nstepien]

Clicking anywhere on the grid triggers the blur event on the focus sink, which we then focus immediately after, triggering the focus handler, so that might not be desired.
We can prevent blur by preventDefault()ing the mousedown event, but that'll break other stuff as well.
Not sure if this is doable.