Prepare changelog for v0.12.3-rc.2

Author: dbkr

CHANGELOG.md

@@ -1,3 +1,9 @@
+Changes in [0.12.3-rc.2](https://github.com/matrix-org/matrix-react-sdk/releases/tag/v0.12.3-rc.2) (2018-04-25)
+===============================================================================================================
+[Full Changelog](https://github.com/matrix-org/matrix-react-sdk/compare/v0.12.3-rc.1...v0.12.3-rc.2)
+
+ * Fix npm packaging
+
 Changes in [0.12.3-rc.1](https://github.com/matrix-org/matrix-react-sdk/releases/tag/v0.12.3-rc.1) (2018-04-25)
 ===============================================================================================================
 [Full Changelog](https://github.com/matrix-org/matrix-react-sdk/compare/v0.12.2...v0.12.3-rc.1)