added verionadded note

Author: yceruto

bundles/best_practices.rst

@@ -82,6 +82,12 @@ The basic directory structure of an AcmeBlogBundle must read as follows:
     ├── LICENSE
     └── README.md
 
+.. versionadded:: 4.4
+
+    This directory convention was introduced in Symfony 4.4 and can be used only when requiring
+    ``symfony/http-kernel`` 4.4 or superior.
+
+
 and the bundle path must be adjusted to the root directory::
 
     class AcmeBlogBundle extends Bundle