owncloud/core

Enhancement: Added needed code for webp thumbnail generation to occur

Previously thumbnail previews for image files of the webp format with the
.webp extension were not generated.  Instead a generic placeholder icon was
shown.  This enhancement/fix caused the generation of preview thumbnails,
just as was standard with other image formats.

https://github.com/owncloud/core/issues/39358
https://github.com/owncloud/core/pull/39360