Prepare changelog for v1.4.0-rc.3

Author: RiotRobot

CHANGELOG.md

@@ -1,3 +1,13 @@
+Changes in [1.4.0-rc.3](https://github.com/matrix-org/matrix-react-sdk/releases/tag/v1.4.0-rc.3) (2019-07-15)
+=============================================================================================================
+[Full Changelog](https://github.com/matrix-org/matrix-react-sdk/compare/v1.4.0-rc.2...v1.4.0-rc.3)
+
+ * Check content and content.users in power levels
+   [\#3223](https://github.com/matrix-org/matrix-react-sdk/pull/3223)
+ * Take adjacent invisible events into account for read receipt, even if any
+   but first should be ignored.
+   [\#3222](https://github.com/matrix-org/matrix-react-sdk/pull/3222)
+
 Changes in [1.4.0-rc.2](https://github.com/matrix-org/matrix-react-sdk/releases/tag/v1.4.0-rc.2) (2019-07-12)
 =============================================================================================================
 [Full Changelog](https://github.com/matrix-org/matrix-react-sdk/compare/v1.4.0-rc.1...v1.4.0-rc.2)