Add a JS package to handle ABI encoding/decoding

[TomAFrench]

Problem

Currently acvm_js assumes that the caller can provide an initial witness with which to execute the circuit.

This is fine for relatively simple programs but it's not a good experience and makes more complex noir programs unwieldy to work with.

Happy Case

In order to interact with Noir programs in the browser we need a way to construct the initial witness from a set of inputs similar to what we have in Prover.toml.

Alternatives Considered

No response

Additional Context

No response

Would you like to submit a PR for this Issue?

Yes

Support Needs

No response

[Savio-Sou]

Add a JS package

Is there any value for it to live as a standalone package? Would it make sense to merge it into noir_wasm or acvm_js?

[TomAFrench]

Neither of those two packages are good spots for this functionality to live tbh.

noir_wasm: This would require a user to load a complete copy of the noir compiler in order to construct initial witnesses.
acvm_js: See noir-lang/acvm-simulator#4

[Savio-Sou]

Hmm reasonable.

The need for wrapping everything into one Noir.js package as an option seems to be growing. Fiddling with 4+ packages just to get started sounds like a DevEx nightmare.