docs: what's new in v5.2

docs/sources/guides/whats-new-in-v5-2.md

++++
+title = "What's New in Grafana v5.2"
+description = "Feature & improvement highlights for Grafana v5.2"
+keywords = ["grafana", "new", "documentation", "5.2"]
+type = "docs"
+[menu.docs]
+name = "Version 5.2"
+identifier = "v5.2"
+parent = "whatsnew"
+weight = -8
++++
+
+# What's New in Grafana v5.2
+
+Grafana v5.2 brings new features, many enhancements and bug fixes. This article will detail the major new features and enhancements.
+
+* [Elasticsearch alerting]({{< relref "#elasticsearch-alerting" >}}) it's finally here!
+* [Cross platform build support]({{< relref "#cross-platform-build-support" >}}) enables native builds of Grafana for many more platforms!
+* [Improved Docker image]({{< relref "#improved-docker-image" >}}) with support for docker secrets
+* [Prometheus]({{< relref "#prometheus" >}}) with alignment enhancements
+* [Alerting]({{< relref "#alerting" >}}) with alert notification channel type for Discord
+* [Dashboards & Panels]({{< relref "#dashboards-panels" >}})
+
+## Elasticsearch alerting
+
+{{< docs-imagebox img="/img/docs/v52/elasticsearch_alerting.png" max-width="800px" class="docs-image--right" >}}
+
+Grafana v5.2 ships with an updated Elasticsearch datasource with support for alerting. Alerting support for Elasticsearch has been one of
+the most requested features by our community and now it's finally here. Please try it out and let us know what you think.
+
+<div class="clearfix"></div>
+
+## Cross platform build support
+
+Grafana v5.2 brings an improved build pipeline with cross platform support. This enables native builds of Grafana for ARMv7 (x32), ARM64 (x64),
+MacOS/Darwin (x64) and Windows (x64) in both stable and nightly builds.
+
+We've been longing for native ARM build support for a long time. With the help from our amazing community this is now finally available.
+
+## Improved Docker image
+
+The Grafana docker image now includes support for Docker secrets which enables you to supply Grafana with configuration through files. More
+information in the [Installing using Docker documentation](/installation/docker/#reading-secrets-from-files-support-for-docker-secrets).
+
+## Prometheus
+
+The Prometheus datasource now aligns the start/end of the query sent to Prometheus with the step, which ensures PromQL expressions with *rate*
+functions get consistent results, and thus avoid graphs jumping around on reload.
+
+## Alerting
+
+By popular demand Grafana now includes support for an alert notification channel type for [Discord](https://discordapp.com/).
+
+## Dashboards & Panels
+
+### Modified time range and variables are no longer saved by default
+
+{{< docs-imagebox img="/img/docs/v52/dashboard_save_modal.png" max-width="800px" class="docs-image--right" >}}
+
+Starting from Grafana v5.2 a modified time range or variable are no longer saved by default. To save a modified
+time range or variable you'll need to actively select that when saving a dashboard, see screenshot.
+This should hopefully make it easier to have sane defaults of time and variables in dashboards and make it more explicit
+when you actually want to overwrite those settings.
+
+<div class="clearfix"></div>
+
+## Changelog
+
+Checkout the [CHANGELOG.md](https://github.com/grafana/grafana/blob/master/CHANGELOG.md) file for a complete list
+of new features, changes, and bug fixes.