Add link to new "Develop Volto add-ons" section (#1755)

* Add link to new "Develop Volto add-ons" section

* Fix heading

Author: stevepiercy

docs/admin-guide/add-ons.md

@@ -15,8 +15,7 @@ This chapter explains how to install {term}`add-ons <add-on>` as Python packages
 
 ```{note}
 The Volto frontend has its own system of add-ons using Node.js packages.
-% TODO: update the following link after https://github.com/plone/volto/pull/6397 is merged to point to `/development/add-ons/index`.
-See {doc}`/volto/addons/index`.
+See {doc}`/volto/development/add-ons/index`.
 ```
 
 
@@ -133,7 +132,7 @@ Follow the upgrade information, if present.
 Else click the {guilabel}`Install` button to complete installation of the add-on.
 
 
-## with Buildout
+## Buildout
 
 Use the following instructions if you installed Plone with Buildout.