Merge branch 'feature_Upgrade-to-TYPO3-11' into 'master'

Classes/Controller/YoutubeController.php

Classes/Hooks/PageLayoutView/PluginRenderer.php

Classes/Preview/PreviewRenderer.php

Classes/Preview/PreviewService.php

Classes/Service/CachedImageService.php

Classes/Service/YoutubeService.php

Configuration/Services.yaml

Configuration/TCA/Overrides/sys_template.php

Configuration/TCA/Overrides/tt_content.php

Configuration/TypoScript/setup.typoscript

README.md

Resources/Public/Icons/Extension.png

Resources/Public/JavaScript/youtubeLightbox.js

UPGRADE.md

composer.json

ext_emconf.php

ext_localconf.php