匹配 iso string duration 语法（PnYnMnDTnHnMnS）

• description: 正则匹配 ISO8601 duration 时间格式 (PnYnMnDTnHnMnS)

  set KEY_DURATION_REG () {
    return /^-?P(?=\w*\d)(?:\d+Y|Y)?(?:\d+M|M)?(?:\d+D|D)?(?:T(?:\d+H|H)?(?:\d+M|M)?(?:\d+(?:\\­.\d{1,2})?S|S)?)?$/
  }

参考文章：

• https://momentjs.com/docs/#/durations/as-iso-string/
• https://github.com/moment/moment/issues/1805#issuecomment-587104197
• https://stackoverrun.com/cn/q/9030614