I remember seeing lua for the browser quite some years ago (not sure if it was fengari or not) that worked similarly (include the script and then anything of type `application/lua` would execute using it). I ran into it in 2014.

If fengari is that, then I think it predates wasm.

Edit: it is not, since my memory is from 2014. However, the git history says fengari was started 5 years ago and wikipedia says wasm came out 4 years ago.