tab(rng, isShift) {
    const cell = dom.ancestor(rng.commonAncestor(), dom.isCell);
    const table = dom.ancestor(cell, dom.isTable);
    const cells = dom.listDescendant(table, dom.isCell);

    const nextCell = lists[isShift ? 'prev' : 'next'](cells, cell);
    if (nextCell) {
      range.create(nextCell, 0).select();
    }
  }
handle tab key

@param {WrappedRange} rng
@param {Boolean} isShift