message: Fix typo in `format` docs
diff: @@ -281,7 +281,7 @@ var unescapedLatinCharacterRegExp = /[a-zA-Z]/
  * 8. `YY` and `YYYY` tokens represent week-numbering years but they are often confused with years.
  * You should enable `options.useAdditionalWeekYearTokens` to use them. See: https://git.io/fxCyr
  *
  - * 9. `D` and `DD` tokens represent days of the year but they are ofthen confused with days of the month.
  + * 9. `D` and `DD` tokens represent days of the year but they are often confused with days of the month.
  * You should enable `options.useAdditionalDayOfYearTokens` to use them. See: https://git.io/fxCyr
  *
  * ### v2.0.0 breaking changes:
  