the weekStart option in locale file seens not work.

Describe the bug A clear and concise description of what the bug is.

const dayjs = require('dayjs')
const weekday = require('dayjs/plugin/weekday')
const locale = {
  weekStart: 1
}
dayjs.locale(locale, null ,true)
dayjs.extend(weekday)

const d1 = dayjs().startOf('week')

const date = d1.toDate()
console.log(date, d1.weekday())

result is ‘2019-08-17T16:00:00.000Z 0’ Expected behavior A clear and concise description of what you expected to happen. 2019-08-18T16:00:00.000Z 1

Information

• Day.js Version [e.g. v1.0.0] 1.8.15
• OS: [e.g. iOS] macOS
• Browser [e.g. chrome 62] node test.js
• Time zone: GMT+8 Asia/Shanghai

[ghost]

import from 'dayjs/locale/en-gb' // weekStart 1
 
dayjs.locale('en-gb').startOf('week').format()

[bilal42011]

This en-gb locale startWeek property is 1 but it is not working …Any solution