docs: restructure guides documentation (#422)

##### SUMMARY

Improve the documentation to have `Guides` at sections, and each part in
the guides files as list item.


![image](https://github.com/ansible-collections/hetzner.hcloud/assets/19195485/ca563056-fbf4-4796-8706-b13faf65f10e)



https://docs.ansible.com/ansible/latest/dev_guide/style_guide/index.html#adding-anchors

docs/docsite/extra-docs.yml

@@ -1,5 +1,5 @@
 ---
 sections:
-  - title: Authentication
+  - title: Guides
     toctree:
-      - authentication
+      - guides

docs/docsite/rst/guides.rst

@@ -1,3 +1,5 @@
+.. _ansible_collections.hetzner.hcloud.docsite.authentication:
+
 Authentication
 ==============