Update CHANGELOG.md

CHANGELOG.md

@@ -37,6 +37,7 @@
 
 ## Tech
 * **Go**: Grafana is now built using golang 1.9
+* **Webpack**: Changed from systemjs to webpack (see readme or building from source guide for new build instructions). Systemjs is still used to load plugins but now plugins can only import a limited set of dependencies. See [PLUGIN_DEV.md](https://github.com/grafana/grafana/blob/master/PLUGIN_DEV.md) for more details on how this can effect some plugins. 
 
 # 4.5.2 (2017-09-22)