Add parallel support

[chronoDave]

Add parallel support

[chronoDave]

After doing experimentation, it seems that a parallel recursive async approach using Promise.all is equally fast if not slower than the iterative serial approach.

// Credits goes to StackOverflow user "qwtel"
// https://stackoverflow.com/a/45130990
const walk = async (root: string): Promise<string[]> => {
  const resolveDir = (dirEnt: fs.Dirent) => {
    if (dirEnt.isDirectory()) return walk(path.resolve(root, dirEnt.name));
    return [path.resolve(root, dirEnt.name)];
  };

  const stack = fs.readdirSync(root, { withFileTypes: true });
  const files = await Promise.all(stack.map(resolveDir));

  return files.flat();
};

type: sync
avg: 116.667 ms (10 runs)
files: 8742
speed: 0.013 ms / file
type: async
avg: 129.819 ms (10 runs)
files: 8742
speed: 0.015 ms / file

Therefore it's not necessary to add an async variant to the project