[TASK] Add Test Image for reading webp images

With official webp support enabled,
reading from webp images can be activated in
EXT:install as well, as "webp" is added to
the default list of "TYPO3_CONF_VARS[GFX][imagefile_ext]

Resolves: #101667
Related: #88537
Releases: main
Change-Id: Ie461c884d48fbc4ed1976bf0ba8967c7281197f0
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82197


Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>