Expose certain functions from `@stellar/js-xdr` so downstream don't need to mix dependencies.

[github-actions[bot]]

Size Change: +3.07 kB (+0.1%)

Total Size: 3.22 MB

Filename	Size	Change
dist/stellar-base.js	2.36 MB	+2.28 kB (+0.1%)
dist/stellar-base.min.js	856 kB	+788 B (+0.09%)

_{compressed-size-action}

[BlaineHeffron]

When I use the cereal namespace instead of just importing directly from js-xdr this code gets a TypeError:

export function processSpecEntryStream(buffer: Buffer) {
  const reader = new cereal.XdrReader(buffer);
  const res: xdr.ScSpecEntry[] = [];
  while (!reader.eof){
    res.push(xdr.ScSpecEntry.read(reader));
  }
  return res;
}

Argument of type 'XdrReader' is not assignable to parameter of type 'Buffer'.
  Type 'XdrReader' is missing the following properties from type 'Buffer': write, toJSON, equals, compare, and 91 more.

93     res.push(xdr.ScSpecEntry.read(reader));

Edit: it still works when I just ts-ignore it, but not sure why it complains when I use the cereal namespace vs importing it directly. Anyway, I don't think its really a problem.