Feature: #85607 - New ThumbnailViewHelper to render thumbnails deferred

See Issue #85607

Description

A new ViewHelper for the backend to render thumbnails deferred was introduced.

The \TYPO3\CMS\Backend\ViewHelpers\ThumbnailViewHelper extends the ImageViewHelper and generates the image tag with the special URI.

<be:thumbnail image="{file.resource}" maxWidth="{thumbnail.width}" maxHeight="{thumbnail.height}" />

Impact

Thumbnails do not block the rendering of a page, because the processing runs an extra http request.