Prepare changelog for v1.7.9

Author: RiotRobot

CHANGELOG.md

@@ -1,3 +1,9 @@
+Changes in [1.7.9](https://github.com/vector-im/element-web/releases/tag/v1.7.9) (2020-10-12)
+=============================================================================================
+[Full Changelog](https://github.com/vector-im/element-web/compare/v1.7.9-rc.1...v1.7.9)
+
+ * Upgrade to React SDK 3.6.0 and JS SDK 8.5.0
+
 Changes in [1.7.9-rc.1](https://github.com/vector-im/element-web/releases/tag/v1.7.9-rc.1) (2020-10-07)
 =======================================================================================================
 [Full Changelog](https://github.com/vector-im/element-web/compare/v1.7.8...v1.7.9-rc.1)