WASM host functions

[jponge]

Hi,

I've been playing with the WASM support but I haven't found how to expose host functions to WASM modules (e.g., my host Java process defines some hello() function and a WASM module can call it).

I have also played with GraalJS and the WebAssembly API, but I couldn't find how to enable WASI here, even with the wasm.Builtins context option.

Thanks!