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/menu.yaml

@@ -1,6 +1,8 @@
 - name: Getting started
   link: /guides/
   children:
+  - name: What is Grafana?
+    link: /guides/what-is-grafana/
   - name: Getting started
     link: /guides/getting_started/
   - name: Intro to time series
@@ -68,7 +70,7 @@
     - link: /permissions/dashboard_folder_permissions/
       name: Dashboard and Folder
     - link: /permissions/datasource_permissions/
-      name: Datasource
+      name: Data source
   - name: Grafana CLI
     link: /administration/cli/
   - name: Internal metrics
@@ -141,6 +143,8 @@
   - name: Data Sources
     link: /features/datasources/
     children:
+    - link: /features/datasources/add-data-source/
+      name: Add data source
     - link: /features/datasources/cloudwatch/
       name: AWS Cloudwatch
     - link: /features/datasources/azuremonitor/
@@ -168,7 +172,7 @@
     - link: /features/datasources/prometheus/
       name: Prometheus
     - link: /features/datasources/testdata/
-      name: Testdata
+      name: TestData DB
   - name: Explore
     link: /features/explore/
   - name: Alerting