feat: add the xmls:i18n domain definition

Author: erral

templates/add-ons/backend/{{ cookiecutter.__folder_name }}/src/packagename/profiles/default/controlpanel.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<object name="portal_controlpanel">
+<object name="portal_controlpanel" xmlns:i18n="http://xml.zope.org/namespaces/i18n">
 
 <!-- -*- extra stuff goes here -*- -->