Revisions from technical writing team

Reduce pixel size of images, then run through pngquant to compress
file size on disk. Also provide documentation edits for tone / style.

doc/operations/incident_management/incidents.md

@@ -163,6 +163,19 @@ Beneath the highlight bar, GitLab displays a summary that includes the following
 Comments are displayed in threads, but can be displayed chronologically
 [in a timeline view](#timeline-view).
 
+### Metrics
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/235994) in [GitLab Premium](https://about.gitlab.com/pricing/) 13.8.
+
+In many cases, incidents are associated to metrics. You can upload screenshots of metric
+charts in the **Metrics** tab:
+
+![Incident Metrics tab](img/incident_metrics_tab_v13_8.png)
+
+When you upload an image, you can associate it with a URL to the original graph. Users can access the original graph by clicking the image:
+
+![Metric image URL dialog](img/metric_image_url_dialog_v13_8.png)
+
 ### Alert details
 
 Incidents show the details of linked alerts in a separate tab. To populate this