Docs: Add cron option for time regions (#101021)

docs/sources/dashboards/build-dashboards/annotate-visualizations/index.md

@@ -209,3 +209,7 @@ When adding or editing an annotation, you can define a repeating time region by
 The above configuration produces the following result in the Time series panel:
 
 {{< figure src="/media/docs/grafana/screenshot-grafana-10-0-timeseries-time-regions.png" max-width="600px" alt="Time series visualization with time regions business hours" >}}
+
+Toggle the **Advanced** switch and use [Cron syntax](https://crontab.run/) to set more granular time region controls. The following example sets a time region of 9:00 AM, Monday to Friday:
+
+{{< figure src="/media/docs/grafana/dashboards/screenshot-annotations-cron-option-v11.6.png" max-width="600px" alt="Time region query with cron syntax" >}}