Prepare changelog for v1.5.3

CHANGELOG.md

+Changes in [1.5.3](https://github.com/matrix-org/matrix-react-sdk/releases/tag/v1.5.3) (2019-09-16)
+===================================================================================================
+[Full Changelog](https://github.com/matrix-org/matrix-react-sdk/compare/v1.5.3-rc.3...v1.5.3)
+
+ * Release: Directory should use the alias or server information to join the
+   room
+   [\#3448](https://github.com/matrix-org/matrix-react-sdk/pull/3448)
+
 Changes in [1.5.3-rc.3](https://github.com/matrix-org/matrix-react-sdk/releases/tag/v1.5.3-rc.3) (2019-09-13)
 =============================================================================================================
 [Full Changelog](https://github.com/matrix-org/matrix-react-sdk/compare/v1.5.3-rc.2...v1.5.3-rc.3)