[FEATURE] Add webp support for GifBuilder

It is now possible - if PHP was compiled with gdlib
that supports webp (available since PHP 7.1), to generate
webp files via GifBuilder.

Example:

page.10 = IMAGE
page.10 {
  file = GIFBUILDER
  file {
    backColor = yellow
    XY = 1024,199
    format = webp
    quality = 44

    10 = IMAGE
    10.offset = 10,10
    10.file = 1:/backimage.jpg
  }
}

Resolves: #102177
Releases: main
Change-Id: I48dac569da5904b4871ee2ad3b3759c54004e8c0
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81417


Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Andreas Kienast <a.fernandez@scripting-base.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Andreas Kienast <a.fernandez@scripting-base.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Benni Mack <benni@typo3.org>