Merge branch '5.4' into 6.0

* 5.4:
  Minor reword
  Update configuration.rst
  move versionadded directive out of list item

Author: javiereguiluz

configuration.rst

@@ -461,6 +461,13 @@ files directly in the ``config/packages/`` directory.
                 webpack_encore:
                     strict_mode: false
 
+            # YAML syntax allows to reuse contents using "anchors" (&some_name) and "aliases" (*some_name).
+            # In this example, 'test' configuration uses the exact same configuration as in 'prod'
+            when@prod: &webpack_prod
+                webpack_encore:
+                    # ...
+            when@test: *webpack_prod
+
         .. code-block:: xml
 
             <!-- config/packages/webpack_encore.xml -->