ToObject
ToObject 添加 `.toObject()` API 以返回带有日期属性的 `object`。
var toObject = require('dayjs/plugin/toObject')
dayjs.extend(toObject)
dayjs('2019-01-25').toObject()
/* { years: 2019,
months: 0,
date: 25,
hours: 0,
minutes: 0,
seconds: 0,
milliseconds: 0 } */