[TASK] Allow rendering of description for InputSlugElement

The description must be available for the InputSlugElement as well to give
editors an additional guidance.

Resolves: #86720
Releases: master
Change-Id: Iaa70a6e62209eb72cbe51be91727c8bed775fac6
Reviewed-on: https://review.typo3.org/58681


Reviewed-by: Riny van Tiggelen <info@online-gamer.nl>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Joerg Kummer <typo3@enobe.de>
Reviewed-by: Jürgen Heym <juergen.heym@hof-university.de>
Tested-by: Jürgen Heym <juergen.heym@hof-university.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>