[TASK] Add scroll-padding to .module-body

This fixes the small annoyance when expanding an item in the
TypoScript Object Browser and the iframe reloads and scrolls to the
expanded item while the doc-header hides this item. CSS scroll-padding
solves this problem for modern browsers.

Resolves: #89217
Releases: master,9.5
Change-Id: If4b71c7fb6ba003b23cdd79460540f0bf335abb8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/61770


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Frank Nägler <frank.naegler@typo3.org>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Frank Nägler <frank.naegler@typo3.org>