docs: function lookup(tags, ranges, defaultValue = null) {
    if (!tags || !ranges) return defaultValue;
  
    tags = Array.isArray(tags) ? tags : [tags];
    ranges = Array.isArray(ranges) ? ranges : [ranges];
  
    for (let i = 0; i < ranges.length; i++) {
      // If the language range "*" is followed by other
      // language ranges, it is skipped.
      if (ranges[i] === '*') continue;
      const match = tags.find(tag =>
        check(tag.toLowerCase(), ranges[i].toLowerCase()),
      );
      if (match) return match;
    }
    // If no language tag matches the
    // request, the "default" value is returned.
    return defaultValue;
  }