message: Add changelog entries for `sub` and `Duration`
diff: @@ -25,6 +25,8 @@ Thanks to [@mborgbrant](https://github.com/mborgbrant), [@saintplay](https://git
  - [Added `inclusive` option to `areIntervalsOverlapping](https://github.com/date-fns/date-fns/pull/643).
  - [Added `isExists` function that checks if the given date is exists](https://github.com/date-fns/date-fns/pull/682).
  - [Added `add` function to add seconds, minutes, hours, weeks, years in single call](https://github.com/date-fns/date-fns/pull/1581).
  +- [Added `sub` function, the opposite of `add`](https://github.com/date-fns/date-fns/pull/1583).
  +- [Added `Duration` type used in `add` and `sub`](https://github.com/date-fns/date-fns/pull/1583).
  - [Added Azerbaijani (az) locale](https://github.com/date-fns/date-fns/pull/1547).
  - [Added Moroccan Arabic (ar-MA) locale](https://github.com/date-fns/date-fns/pull/1578).
  