changelog: add notes about closing #15291

CHANGELOG.md

@@ -7,6 +7,7 @@
 * **Cloudwatch**: Add AWS/Neptune metrics [#14231](https://github.com/grafana/grafana/issues/14231), thx [@tcpatterson](https://github.com/tcpatterson)
 * **Cloudwatch**: Add AWS RDS ServerlessDatabaseCapacity metric [#15265](https://github.com/grafana/grafana/pull/15265), thx [@larsjoergensen](https://github.com/larsjoergensen)
 * **Annotations**: Support PATCH verb in annotations http api [#12546](https://github.com/grafana/grafana/issues/12546), thx [@SamuelToh](https://github.com/SamuelToh)
+* **Templating**: Add json formatting to variable interpolation [#15291](https://github.com/grafana/grafana/issues/15291), thx [@mtanda](https://github.com/mtanda)
 
 # 6.0.0-beta1 (2019-01-30)