message: Fix typo in i18n documentation
diff: ## Usage
  **Important! Note that non-CommonJS packages (Bower, CDN)
  -don't support I18 yet.** Please [vote for the issue](https://github.com/date-fns/date-fns/issues/232)
  +don't support I18n yet.** Please [vote for the issue](https://github.com/date-fns/date-fns/issues/232)
  if you want to make it happen.
  There are just a few functions that support I18n:
  