NodeJS bindings

[dgcoffman]

This PR adds NodeJS bindings with the following interface:

  loadTrustedSetup: (filePath: string) => SetupHandle;

  freeTrustedSetup: (setupHandle: SetupHandle) => void;

  blobToKzgCommitment: (blob: Blob, setupHandle: SetupHandle) => KZGCommitment;

  computeAggregateKzgProof: (
    blobs: Blob[],
    setupHandle: SetupHandle
  ) => KZGProof;

  verifyAggregateKzgProof: (
    blobs: Blob[],
    expectedKzgCommitments: KZGCommitment[],
    kzgAggregatedProof: KZGProof,
    setupHandle: SetupHandle
  ) => boolean;

  // Not used in 4844(?), not exported and not covered with test automation. But I think it probably works.
  verifyKzgProof: (
    polynomialKzg: KZGCommitment,
    z: BLSFieldElement,
    y: BLSFieldElement,
    kzgProof: KZGProof,
    setupHandle: SetupHandle
  ) => boolean;

I also added blst as a submodule.

Most of diff is a yarn lockfile.

Test instructions: README

[dgcoffman]

This is the interface of the JavaScript module which can be imported by a NodeJS program. node-gyp turns this into kzg.node.

[Inphi]

might not matter, but should this be set to the vector capacity rather than length? I dunno of any stdlib that uses a different capacity at construction tho.

[dgcoffman]

I see what you mean and I think it should be the byte length supplied to the function, not the allocation for the vector, even in the case where they differ

[Inphi]

might as well wrap these in a vector to avoid manually (and possibly forgetting to) freeing the allocation.

[dgcoffman]

I tried for an hour and I don't think it's possible to make a std::vector<Blob>. https://stackoverflow.com/questions/16970624/cant-make-a-vector-of-fixed-size-arrays

Do you know how to do it? I think I want to just manage the memory manually.

[dgcoffman]

The error is

error: object expression of non-scalar type 'unsigned char[131072]' cannot be used in a pseudo-destructor expression

[Inphi]

Oh interesting that Blob is typedef'd directly as a fixed-array. Yeah that won't work.
@xrchz perhaps we could redefine these types as structs like how blst does it here. This makes it more obvious that the types are arrays and lets the C++ compiler know that they're trivially copyable.

[xrchz]

Sure I can do it that way instead!

[xrchz]

Actually I don't really understand how to use those structs. Do you?

[xrchz]

I tried a version of this on a new branch, struct_blob, ptal.

[dgcoffman]

Moving to dankrad#3