It should be possible to encode your sample soundfiles (or any other files) as base64 and include the files in the .csd file using … tags. I have attached a working example.
Of course the resulting .csd file could become quite large, but I don’t think that will actually stop it from working.
This doesn’t work in the Csound Web-IDE, it looks like the Web IDE editor messes with the encoded text. But it works fine with my build of Csound for WebAssembly if you paste the attached example into this: https://gogins.github.io/player.html