Feature: #65698 - Additional localization files in backend workspace module

See Issue #65698

Description

The AdditionalResourceService of the workspace module in the backend is extended by the functionality to register custom localization files that are forwarded to the PageRenderer in the end. This way, labels can be accessed in JavaScript using the TYPO3.l10n.localize() function for instance.

\TYPO3\CMS\Workspaces\Service\AdditionalResourceService::getInstance()->addLocalizationResource(
        'EXT:my_extension/Resources/Private/Language/locallang.xlf'
);