I'm working on a little site called WGSL Toy, here: https://wgsltoy.com/
It's basically like ShaderToy but for WebGPU instead of WebGL. I started it as I have been doing some Rust + wgpu development for art projects and I need a easy way to play around with shaders.
It's very early in development - you can go and just use it right now. But soon I want to support creating an account, saving / sharing shaders, and eventually go beyond the featureset of ShaderToy by allowing for custom input images / textures.
Code is on github: https://github.com/sdedovic/wgsltoy