localizedFormat plugin is interpolating content inside square brackets

[mariomc]

Describe the bug
localizedFormat plugin is changing/interpolating content inside square brackets

const dayJSformat = dayjs.format('[L]') // outputs: 29/03/2019
const momentFormat = moment.format('[L]') // outputs [L]
expect(dayJSformat).toEqual(momentFormat) // throws

Expected behavior
localizedFormat plugin should uphold behavior of the original format method and not change/interpolate content inside square brackets

Information

• Day.js Version: all
• OS: all
• Browser: all

[mariomc]

If you want, i'll include this fix inside #546

[ghost]

Sounds good

[iamkun]

#546