Hi,
HikaShop does not currently supports the upload of webp images.
HikaShop has an option "Generate WebP images" that you can activate for webp images to be generated from he png/jpg images you've added to your products. That way, for browsers supporting the webp format, the webp images will be used, while for older browsers, the original png/jpg image will be used.
However, teh webp format is now widely supported. So with next version of HikaShop, the webp format will be supported for the upload of images too.