Support WASI execution

[twitchyliquid64]

Saw this on HN: https://hacks.mozilla.org/2019/03/standardizing-wasi-a-webassembly-system-interface/

We should consider implementing a package that exposes the WASI API.

[sbinet]

yep, definitely.

[sbinet]

something to look at, too:

• wasm: support new WASI interface golang/go#31105

[twitchyliquid64]

I'm thinking of doing the following:

• Making a new subpackage: github.com/go-interpreter/wagon/wasi
• This package exposes a wasi.MakeHostEnvironment
• You pass host.WASIResolver as the wasm.ResolveFunc in a call to wasm.ReadModule, which will load the specified module + resolve the WASI imports for you.

Thoughts?

[twitchyliquid64]

This is also a relevant doc, which enumerates the API surface we need to provide to support WASI.

[sbinet]

SGTM.