Getting Started section rehaul (#28090)

* Updated Getting Started topic, based on feedback from Diana and Daniel. Added 2 entries to Glassry.

* Added new topic Getting Started with Grafana and Prometheus

* Corrected image path. A couple of other minor changes.

* Updated image link based on Marcus's suggestion.

* Updated topics based on feedback.

* Update docs/sources/getting-started/getting-started.md

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

* Update docs/sources/getting-started/getting-started.md

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

* Added Diana's latest changes.

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

docs/sources/menu.yaml

@@ -3,8 +3,10 @@
   children:
     - name: What is Grafana?
       link: /getting-started/what-is-grafana/
-    - name: Getting started
+    - name: With Grafana
       link: /getting-started/getting-started/
+    - name: With Grafana and Prometheus
+      link: /getting-started/getting-started-prometheus/
     - name: Intro to time series
       link: /getting-started/timeseries/
     - name: Time series dimensions