Demoboard would work just as well. It's just about how you set up the examples. One moment ... let me make an example without a server side toolchain involved ...
Here we go:
https://frontarm.com/demoboard/?id=321f4d83-b0d8-4bd0-876b-0...
No more hidden magic. Everything happens in the browser. The user can use the downloaded thing without setting up a server side toolchain.