message: Add changelog entry for isExists
diff: @@ -10,12 +10,13 @@ This change log follows the format documented in [Keep a CHANGELOG].
  ## Unreleased
  -Thanks to [@mborgbrant](https://github.com/mborgbrant), [@saintplay](https://github.com/saintplay).
  +Thanks to [@mborgbrant](https://github.com/mborgbrant), [@saintplay](https://github.com/saintplay), [@mrenty](https://github.com/mrenty).
  ### Added
  - [Added `eachMonthOfInterval` and `eachYearOfInterval`](https://github.com/date-fns/date-fns/pull/618).
  - [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]().
  ## [2.8.1] - 2019-11-22
  