added missing breaking change warning to changelog

Author: mtrezza

CHANGELOG.md

@@ -9,7 +9,7 @@
 - Removed unused config parameter from docs. [#1](https://github.com/mtrezza/parse-server-api-mail-adapter/pull/1). Thanks to [mtrezza](https://github.com/mtrezza)
 
 ### 🧬 Improvements
-- Added locale to API callback. [#2](https://github.com/mtrezza/parse-server-api-mail-adapter/pull/2). Thanks to [mtrezza](https://github.com/mtrezza)
+- ⚠️ Added locale to API callback. This is a breaking change because the `apiCallback` now returns an object `{payload, locale}` instead of only the `payload`. [#2](https://github.com/mtrezza/parse-server-api-mail-adapter/pull/2). Thanks to [mtrezza](https://github.com/mtrezza)
 - Added badges to readme. [#3](https://github.com/mtrezza/parse-server-api-mail-adapter/pull/3). Thanks to [mtrezza](https://github.com/mtrezza)
 
 # 1.0.0