feat: impl revparse, commit, signature, object

[seokju-na]

Add rev-parse feature.

import { openRepository, revparseModeContains, RevparseMode } from 'es-git';

const repo = await openRepository('...');
const spec = repo.revparse('main..other');
revparseModeContains(
  spec.mode,
  RevparseMode.Range
); // true