Add new explore/observability related features to whats new docs (#27540)

* Add new explore/observability related features to whats new docs

* Apply suggestions from code review

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Address review comments

* Update docs/sources/guides/whats-new-in-v7-2.md

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Change new loki feature title

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

docs/sources/guides/whats-new-in-v7-2.md

@@ -23,6 +23,9 @@ The main highlights are:
   - [**Added table column filters**]({{< relref "#added-table-column-filters" >}})
   - [**New field override selection options**]({{< relref "#new-field-override-selection-options" >}})
 - [**New transformations and enhancements**]({{< relref "#new-transformations-and-enhancements" >}})
+- [**Inspect queries in Explore**]({{< relref "#inspect-queries-in-explore" >}})
+- [**$__rate_interval for Prometheus**]({{< relref "#__rate_interval-for-prometheus" >}})
+- [**Toggle parsed Loki fields**]({{< relref "#toggle-parsed-loki-fields" >}})
 - [**Sensitive alert channel settings are now encrypted**]({{< relref "#sensitive-alert-channel-settings-are-now-encrypted" >}})
 - [**Grafana Enterprise features**]({{< relref "#grafana-enterprise-features" >}})
   - [**Report time range**]({{< relref "#report-time-range" >}})
@@ -81,6 +84,20 @@ Grafana 7.2 includes the following transformation enhancements:
 
 {{< docs-imagebox img="/img/docs/v72/transformations.gif" max-width="800px" caption="Group by and reordering of transformations" >}}
 
+## Inspect queries in Explore
+
+You can enjoy all the details query inspector gave you in dashboards now in Explore as well. You can open query inspector tab with the button next to query history. See [Query inspector in Explore]({{< relref "../features/explore/index.md#query-inspector" >}}) for more details.
+
+## \$\_\_rate_interval for Prometheus
+
+You can now use the new variable `$__rate_interval` in Prometheus for rate functions mainly. `$__rate_interval` in general is one scrape interval larger than `$__interval` but is never smaller than four times the scrape interval (which is 15s by default). See the [Prometheus data source]({{< relref "../features/datasources/prometheus.md#using-__rate_interval-variable" >}}) for more details.
+
+## Toggle parsed Loki fields
+
+With this awesome contribution from one of our community members, you can now toggle parsed fields in Explore.
+
+{{< docs-imagebox img="/img/docs/v72/explore-toggle-parsed-fields.gif" max-width="800px" caption="Toggling parsed fields in Explore" >}}
+
 ## Sensitive alert channel settings are now encrypted
 
 Alert notification channels now store sensitive settings and secrets, such as API tokens and passwords, encrypted in the database.