Setting Timezone adds an extra hour

[mr-short]

Describe the bug
There seems to be an extra hour being added when setting timezones:

dayjs.utc('2021-01-01').toString()                                 // 'Fri, 01 Jan 2021 00:00:00 GMT'
dayjs.utc('2021-01-01').tz('America/Chicago').toString()           // 'Fri, 01 Jan 2021 01:00:00 GMT'
dayjs.utc('2021-01-01').tz('America/Chicago', false).toString()    // 'Fri, 01 Jan 2021 01:00:00 GMT'
dayjs.utc('2021-01-01').tz('America/Chicago', true).toString()     // 'Fri, 01 Jan 2021 07:00:00 GMT'  should be 06

Seems to be related to daylight savings time, as it only appears half the year:

dayjs.utc('2021-01-01').tz('America/Chicago')
                       .tz('America/Chicago')
                       .tz('America/Chicago')
                       .tz('America/Chicago').toString()           // 'Fri, 01 Jan 2021 04:00:00 GMT'
dayjs.utc('2021-07-01').tz('America/Chicago')
                       .tz('America/Chicago')
                       .tz('America/Chicago')
                       .tz('America/Chicago').toString()           // 'Thu, 01 Jul 2021 00:00:00 GMT'

Expected behavior

That it works like momentjs:

dayjs('2021-01-01').tz('America/Chicago').toISOString()   // '2021-01-01T07:00:00.000Z'
moment('2021-01-01').tz('America/Chicago').toISOString()  // '2021-01-01T06:00:00.000Z'

Information

• Day.js Version [v1.10.7, from day.js.org]
• OS: [Linux/Ubuntu]
• Browser [Chrome Version 94.0.4606.81 (Official Build) (64-bit)]
• Time zone: [GMT-06:00 DST (Central Daylight Time)]

[mr-short]

Looks like there's a PR that has been out for awhile that fixes this issue: #1448