Fix label and reorient where the comments are.

Author: Rudd-O

docs/install/containers/images/backend.md

@@ -65,13 +65,6 @@ Plone 6 example:
 docker run -p 8081:8081 -e LISTEN_PORT=8081 plone/plone-backend:{PLONE_BACKEND_VERSION}
 ```
 
-#### Adding configuration to `zope.conf` or additional ZCML
-
-With the standard container, it is not possible to add configuration fragments to
-`zope.conf` directly or add extra ZCML, like it is with the `buildout` deployment
-method.  However, you can derive your own container image, and drop in configuration
-fragments.  See {ref}`backend-extending-from-this-image-label` below for instructions.
-
 ### Site creation variables
 
 | Environment variable | Description |
@@ -263,6 +256,16 @@ We advise against using this feature on production environments.
 In this case, extend the image as explained before.
 ```
 
+#### Adding configuration to `zope.conf` or additional ZCML
+
+Some Plone add-ons require changes to `zope.conf` or extra ZCML.
+
+With the standard container, it is not possible to add configuration fragments to
+`zope.conf` directly or add extra ZCML, like it is with the `buildout` deployment
+method.
+
+However, you can derive your own container image, and drop in configuration
+fragments.  See {ref}`backend-extending-from-this-image-label` below for instructions.
 
 (containers-images-backend-developing-packages-label)=
 
@@ -286,6 +289,7 @@ docker run -p 8080:8080 -e DEVELOP="/app/src/mysite.policy" -v /path/to/mysite.p
 We advise against using this feature on production environments.
 ```
 
+(backend-extending-from-this-image-label)=
 
 ## Extending from this image