[doc] Timezone example doesn't work

The example code for using timezones in date-fns 2.x doesn’t work:

> npm install date-fns date-fns-timezone

const { zonedTimeToUtc, utcToZonedTime, format } = require('date-fns-tz')

// Set the date to "2018-09-01T16:01:36.386Z"
const utcDate = zonedTimeToUtc('2018-09-01 18:01:36.386', 'Europe/Berlin')

// Obtain a Date instance that will render the equivalent Berlin time for the UTC date 
const date = new Date('2018-09-01Z16:01:36.386Z')
const timeZone = 'Europe/Berlin'
const zonedDate = utcToZonedTime(date, timeZone)
// zonedDate could be used to initialize a date picker or display the formatted local date/time

// Set the output to "1.9.2018 18:01:36.386 GMT+02:00 (CEST)"
const pattern = 'D.M.YYYY HH:mm:ss.SSS [GMT]Z (z)'
const output = format(zonedDate, pattern, { timeZone })

[...]/test.js:4
const utcDate = zonedTimeToUtc('2018-09-01 18:01:36.386', 'Europe/Berlin')
                ^
TypeError: zonedTimeToUtc is not a function 

Edit: I just noticed that the require in the example code above is inconsistent with the demo code, date-fns-tz instead date-fns-timezone. This seems to come from the outdated date-fns documentation.