speedbase/ext_localconf.php

<?php

use TYPO3\CMS\Core\Information\Typo3Version;
use TYPO3\CMS\Core\Utility\ExtensionManagementUtility;
use TYPO3\CMS\Core\Utility\GeneralUtility;

$versionInformation = GeneralUtility::makeInstance(Typo3Version::class);
// Only include page.tsconfig if TYPO3 version is below 12 so that it is not imported twice.
if ($versionInformation->getMajorVersion() < 12) {
ExtensionManagementUtility::addPageTSConfig('
@import "EXT:speedbase/Configuration/page.tsconfig"
');
}