API Docs: create Authentication page and order sidebar menu (#92900)

* API Docs: create `Authentication` page and order sidebar menu

* fix minor typos

* Update capitalization

We don't capitalize titles as per https://grafana.com/docs/writers-toolkit/write/style-guide/capitalization-punctuation/

* Update docs/sources/developers/http_api/examples/_index.md

Co-authored-by: Jack Baldry <jack.baldry@grafana.com>

* Update docs/sources/developers/http_api/authentication.md

Co-authored-by: Jack Baldry <jack.baldry@grafana.com>

---------

Co-authored-by: Irene Rodriguez <irene.rodriguez@grafana.com>
Co-authored-by: Jack Baldry <jack.baldry@grafana.com>

docs/sources/developers/http_api/examples/_index.md

@@ -0,0 +1,18 @@
+---
+canonical: https://grafana.com/docs/grafana/latest/developers/http_api/examples/
+keywords:
+  - grafana
+  - tutorials
+  - API
+labels:
+  products:
+    - enterprise
+    - oss
+title: 'HTTP API examples'
+menuTitle: 'Examples'
+weight: 02
+---
+
+# HTTP API examples
+
+{{< section >}}