code: function findFile (filename) {
      const file = configDirectory + '/' + filename
      if (fs.existsSync(file)) return file
      const defaultFile = defaultDirectory + '/' + filename
      if (fs.existsSync(defaultFile)) return defaultFile
      return null
    }
docs: Try to find a config file.
  Look first in the configDirectory and then fallback to the defaultDirectory.
  If the file is still not found, return null.