You can support a variety of formats in Safari using WebAssembly builds of the decoders. WebAssembly for audio and image formats is more than fast enough. It's even fast enough for VP9 video.
Is it really worth it to ship a decoder to every user of your site rather than encode it once on your server?
Don't get me wrong, it's a super cool demo but anyone who does this is prod is a little nuts. The exception being a service that's write once read maybe like CCTV cameras.
It's all gravy, the javascript WebP decoders, until you convert your 20K high res photo site to WebP, then not realizing for a week, scratching your head about the bounce rate spiking, that you're crashing browsers left and right...
WebP demo: https://webmproject.github.io/libwebp-demo/webp_wasm/index.h...
Theora\VP8\VP9\Opus\Vorbis demo: https://brionv.com/misc/ogv.js/demo/
ogv.js on GitHub: https://github.com/brion/ogv.js