code: function read(description, options, callback) {
    var file = vfile(description)
  
    if (!callback && typeof options === 'function') {
      callback = options
      options = null
    }
  
    if (!callback) {
      return new Promise(executor)
    }
  
    executor(resolve, callback)
  
    function resolve(result) {
      callback(null, result)
    }
  
    function executor(resolve, reject) {
      var fp
  
      try {
        fp = path.resolve(file.cwd, file.path)
      } catch (error) {
        return reject(error)
      }
  
      fs.readFile(fp, options, done)
  
      function done(error, res) {
        if (error) {
          reject(error)
        } else {
          file.contents = res
          resolve(file)
        }
      }
    }
  }
docs: Create a virtual file and read it in, asynchronously.