docs(): updated changelog

CHANGELOG.md

@@ -1,6 +1,7 @@
 # 3.1.0 (unreleased)
 
 ### Enhancements
+* **Dashboard Export/Import**: Dashboard export now templetize data sources and constant variables, users pick these on import, closes [#5084](https://github.com/grafana/grafana/issues/5084)
 * **Dashboard Url**: Time range changes updates url, closes [#458](https://github.com/grafana/grafana/issues/458)
 * **Dashboard Url**: Template variable change updates url, closes [#5002](https://github.com/grafana/grafana/issues/5002)
 * **Singlestat**: Add support for range to text mappings, closes [#1319](https://github.com/grafana/grafana/issues/1319)