code: function getDirectories(source) {
    const isDirectory = sourcePath => lstatSync(sourcePath).isDirectory()
    return readdirSync(source)
      .map(name => join(source, name))
      .filter(isDirectory)
  }
docs: fetch a list of dirs inside a dir
  
  @param {any} source path of a dir
  @returns {array} list of the dirs inside