https://github.com/maierfelix/dawn-ray-tracing
Yes, chessboard3d.app is written with raw JS APIs and raw WebGPU. It does use the rapier physics library, which uses WASM, which might be an issue? It implements its own ray tracing but would probably run 10x faster with hardware ray tracing support.
I think you'd get a lot of attention if you had hardware ray tracing, since that's only currently available in DirectX 12 and Vulkan, requiring implementation in native desktop platforms. FWIW, if the path looks feasible, I would be interested in contributing.