function _positionForIndex (index) {
    const textTillIndex = el.value.substring(0, index)
    const row = (textTillIndex.match(/\n/g) || []).length + 1
    const col = textTillIndex.length - textTillIndex.lastIndexOf('\n')

    return {
      row,
      column: col
    }
  }
Returns textarea row and column position for certain index
@param {Number} index text index
@returns {{row: Number, column: Number}}