Docs: Plugins doc reorganization, part 1 (#69864)

* Initial commit

* Prettier fixes

* Doc-validator fixes part 1

* Doc-validator fixes part 2

* More doc-validator fixes

* More doc-validator fixes

* Test

* link test

* Linnk test

* Link test

* More fixes

* More fixes

* Doc-validator fixes

* Doc-validator fixes

* fix broken link

* Fix

* Testing

* Doc fixes

* Link fixes

* Fix links

* Update docs/sources/developers/plugins/create-a-grafana-plugin/_index.md

Co-authored-by: David Harris <david.harris@grafana.com>

* Testing

* Testing

* Testing

* Testing

* Doc-validator fixes

* Doc-validator fixes

* Doc-validator fixes

* Fix broken links for plugins reorganization project

* Prettier fixes

* Prettier fixes

* Incorporate reviewer feedback

* Link fixes

* Link fixes

* Link fixes

* Link fix

* Deleted space

* Codeowners fix

* Change grafana.com links to absolute URLs for Hugo

---------

Co-authored-by: David Harris <david.harris@grafana.com>

docs/sources/developers/plugins/create-a-grafana-plugin/extend-a-plugin/_index.md

@@ -0,0 +1,34 @@
+---
+title: Extend a Grafana plugin
+menuTitle: Extend a plugin
+keywords:
+  - grafana
+  - plugins
+  - plugin
+  - development
+  - extension
+  - documentation
+description: An index of how-to topics for extending or enhancing Grafana plugins.
+weight: 200
+---
+
+# Extend a Grafana plugin
+
+This section contains how-to topics for extending or enhancing Grafana plugins:
+
+- [Enable annotations]({{< relref "./add-support-for-annotations.md" >}})
+- [Add anonymous usage reporting]({{< relref "./add-anonymous-usage-reporting.md" >}})
+- [Add authentication for a data source plugin]({{< relref "./add-authentication-for-data-source-plugins.md" >}})
+- [Add distributed tracing for backend plugins]({{< relref "./add-distributed-tracing-for-backend-plugins.md" >}})
+- [Add features to Explore queries]({{< relref "./add-support-for-explore-queries.md" >}})
+- [Add query editor help]({{< relref "./add-query-editor-help.md" >}})
+- [Add support for variables]({{< relref "./add-support-for-variables.md" >}})
+- [Build a custom panel option editor]({{< relref "./custom-panel-option-editors.md" >}})
+- [Use extensions to add links to app plugins]({{< relref "./extend-the-grafana-ui-with-links.md" >}})
+- [Work with cross-plugin links]({{< relref "./cross-plugin-linking.md" >}})
+
+Additional resources:
+
+- [Automate development with CI](https://grafana.github.io/plugin-tools/docs/ci)
+- [Create nested plugins](https://grafana.github.io/plugin-tools/docs/nested-plugins)
+- [Extend configurations](https://grafana.github.io/plugin-tools/docs/advanced-configuration)