Updated Drupal to 8.6. This goes with the following updates because it's possible...

[yaffs-website] / web / core / lib / Drupal / Component / Transliteration / data / dk.php

<?php

/**
 * @file
 * Danish transliteration data for the PhpTransliteration class.
 */

$overrides['dk'] = [
  0xC5 => 'Aa',
  0xD8 => 'Oe',
  0xE5 => 'aa',
  0xF8 => 'oe',
];