/// Find first char which is not a space
/// @access private
/// @param {String} $string - String
/// @param {String} $direction ['left'] - Either `left` or `right`
/// @return {Number}
@function _first-index($string, $direction: 'left') {
  @for $i from 1 through str-length($string) {
    $index: if($direction == 'left', $i, -$i);

    @if str-slice($string, $index, $index) != ' ' {
      @return $index;
    }
  }

  @return 0;
}