📝 Update release notes

docs/en/docs/release-notes.md

@@ -2,6 +2,7 @@
 
 ## Latest changes
 
+* Use `Optional` in all the examples in the docs. Original PR [#1574](https://github.com/tiangolo/fastapi/pull/1574) by [@chrisngyn](https://github.com/chrisngyn), [@kx-chen](https://github.com/kx-chen), [@YKo20010](https://github.com/YKo20010). Updated and merged PR [#1644](https://github.com/tiangolo/fastapi/pull/1644).
 * Update tests and handling of `response_model_by_alias`. PR [#1642](https://github.com/tiangolo/fastapi/pull/1642).
 * Add translation to Chinese for [Body - Fields - 请求体 - 字段](https://fastapi.tiangolo.com/zh/tutorial/body-fields/). PR [#1569](https://github.com/tiangolo/fastapi/pull/1569) by [@waynerv](https://github.com/waynerv).
 * Update Chinese translation of main page. PR [#1564](https://github.com/tiangolo/fastapi/pull/1564) by [@waynerv](https://github.com/waynerv).