Add support for .webp image format

WebP is an image format that utilizes both lossy and lossless compression formats. … WebP offers file sizes that are around 30% smaller than JPEG without a quality gap. It also provides transparency (alpha channel) like PNG, and the ability to animate images like the GIF format.

Images on the web are increasingly .webp format. Would be useful to have the format directly supported within Roon for album covers and artist images.