Docs: New panel editor documentation (#24711)

* Create panel-editor.md

* content updates

* Update panels-overview.md

* Update panel-editor.md

* Update panel-editor.md

* Update menu.yaml

* Update whats-new-in-v7-0.md

* Update docs/sources/panels/panel-editor.md

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

* Update docs/sources/panels/panel-editor.md

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

* Update docs/sources/panels/panel-editor.md

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

* Update docs/sources/panels/panel-editor.md

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

* Update docs/sources/panels/panel-editor.md

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

* Update docs/sources/panels/panel-editor.md

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

* Update _index.md

* Update docs/sources/panels/panel-editor.md

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

* Update docs/sources/panels/panel-editor.md

Co-authored-by: sarlinska <sarlinska@gmail.com>

* Update docs/sources/panels/panel-editor.md

Co-authored-by: sarlinska <sarlinska@gmail.com>

* Update docs/sources/panels/panel-editor.md

Co-authored-by: sarlinska <sarlinska@gmail.com>

* Update docs/sources/panels/panel-editor.md

Co-authored-by: sarlinska <sarlinska@gmail.com>

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>
Co-authored-by: sarlinska <sarlinska@gmail.com>

docs/sources/menu.yaml

@@ -134,6 +134,8 @@
   children:
   - link: /features/panels/panels/
     name: Overview
+  - link: /panels/panel-editor/
+    name: Panel editor
   - link: /features/panels/graph/
     name: Graph
   - link: /features/panels/table_panel/