Docs: Create Intro grafana (#22522)

* Create add-a-data-source.md

* Added links to Add a data source

* Create intro-to-grafana.md

* Updated menu and files

* fixed link

* Update dashboards.md

* Updated enterprise links

* Update _index.md

* Update intro-to-grafana.md

* added content and links

* Update menu.yaml

* fixing links

* fixing links

* Update menu.yaml

* Updated index.md and what is grafana

* changed topic title

* Update getting_started.md

* Updated content

* Update docs/sources/guides/intro-to-grafana.md

Co-Authored-By: Marcus Olsson <accounts+github@marcus.se.net>

* Update docs/sources/guides/intro-to-grafana.md

Co-Authored-By: Marcus Olsson <accounts+github@marcus.se.net>

* Update docs/sources/guides/intro-to-grafana.md

Co-Authored-By: Marcus Olsson <accounts+github@marcus.se.net>

* Update intro-to-grafana.md

* changed file name

* Update _index.md

* Minor edits

* Update menu.yaml

* Update what-is-grafana.md

* Update what-is-grafana.md

* Fix: updates snapshots

* Revert "Fix: updates snapshots"

Co-authored-by: Marcus Olsson <accounts+github@marcus.se.net>
Co-authored-by: Lukas Siatka <lukasz.siatka@grafana.com>

docs/sources/alerting/metrics.md

@@ -11,7 +11,7 @@ weight = 2
 
 # Metrics from the alert engine
 
-The alert engine publishes some internal metrics about itself. You can read more about how Grafana publishes [internal metrics]({{ < "../administration/metrics/" > }}).
+The alert engine publishes some internal metrics about itself. You can read more about how Grafana publishes [internal metrics]({{< relref "../administration/metrics/" >}}).
 
 Description | Type | Metric name
 ---------- | ----------- | ----------