Add package.json converter

[nichtich]

I'm surprised nobody has done it before and I was just about to hack my own script to convert package.json to CITATION.cff to have a single source of truth and avoid crafting and updating CITATION.cff by hand. Maybe I can extend this library instead?

Here is a sketch, just to illustrate the idea:

function parseAuthor(author: string | PackageAuthor): PackageAuthor {
  if (typeof author === 'string') {
    // Pattern: "Name <email> (url)"
    const m = author.match(/^(.*?)\s*(?:<([^>]+)>)?\s*(?:\(([^)]+)\))?/);
    return {
      name: m?.[1]?.trim() || author,
      email: m?.[2] || undefined,
      url: m?.[3] || undefined,
    };
  } else if (typeof author === 'object') {
    return {
      name: author.name,
      email: author.email,
      url: author.url,
      orcid: author.orcid,
    };
  }
  return { name: String(author) };
}

const authors: PackageAuthor[] = [];
if (pkg.author) authors.push(parseAuthor(pkg.author));
if (Array.isArray(pkg.contributors)) {
  for (const c of pkg.contributors) authors.push(parseAuthor(c));
  // TODO add ORCID from another source, e.g. something like https://git-scm.com/docs/gitmailmap
}

const repoUrl = typeof pkg.repository === 'object' ? pkg.repository.url : pkg.repository;

const citation: Record<string, any> = {
  'cff-version': '1.2.0',
  message: 'If you use this software, please cite it using this metadata',
  title: pkg.name, // required
  version: pkg.version, // required
  'date-released': pkg.cff.?release || '', // TODO: get from git history instead
  abstract: pkg.description || '',
  'repository-code': repoUrl.?replace(/^git\+/, '').?replace(/\.git$/, ''),
  type: 'software',
  authors: authors.filter(a => a?.name),
};

This would also solve #1.