/// Returns a list of keys to to pass into the map-set-deep() function
///
/// @author Sam Richard
/// @access public
/// @link https://git.io/vPrlJ
///
/// @param $keys
/// @param $counter
@function get-keys($keys, $counter) {
    $return: ();

    @for $i from 1 to $counter {
        $return: append($return, nth($keys, $i));
    }

    @return $return;
}