Add note to twig docs that the baseUrl must be prepended

doc/providers/twig.rst

@@ -115,10 +115,15 @@ from a template:
 
 .. code-block:: jinja
 
-    {{ render('/sidebar') }}
+    {{ render(app.request.baseUrl ~ '/sidebar') }}
 
     {# or if you are also using UrlGeneratorServiceProvider with the SymfonyBridgesServiceProvider #}
-    {{ render(path('sidebar')) }}
+    {{ render(url('sidebar')) }}
+
+.. note::
+
+    You must prepend the ``app.request.baseUrl`` to render calls to ensure
+    that the render works when deployed into a sub-directory of the docroot.
 
 Traits
 ------