in der eigenen ext_localconf.php wird dies aufgerufen:
call_user_func(static function () {
// Register content element icons
$iconRegistry = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Imaging\IconRegistry::class);
$iconRegistry->registerIcon(
'tx_myaccordion_accordion',
\TYPO3\CMS\Core\Imaging\IconProvider\FontawesomeIconProvider::class,
[
'name' => 'address-card',