Prepare changelog for v0.12.0-rc.5

Author: lukebarnard1

CHANGELOG.md

@@ -1,3 +1,12 @@
+Changes in [0.12.0-rc.5](https://github.com/matrix-org/matrix-react-sdk/releases/tag/v0.12.0-rc.5) (2018-04-09)
+===============================================================================================================
+[Full Changelog](https://github.com/matrix-org/matrix-react-sdk/compare/v0.12.0-rc.4...v0.12.0-rc.5)
+
+ * Added radio button to set group join policy
+ * Fix to prevent guests from accessing lab features
+ * Fix broken forgot password page
+ * Fix crash when joining a room after peeking
+
 Changes in [0.12.0-rc.4](https://github.com/matrix-org/matrix-react-sdk/releases/tag/v0.12.0-rc.4) (2018-03-22)
 ===============================================================================================================
 [Full Changelog](https://github.com/matrix-org/matrix-react-sdk/compare/v0.12.0-rc.3...v0.12.0-rc.4)