Adding one more note about why we're in config.yml

Author: weaverryan

cookbook/logging/channels_handlers.rst

@@ -25,7 +25,8 @@ Switching a Channel to a different Handler
 
 Now, suppose you want to log the ``security`` channel to a different file.
 To do this, just create a new handler and configure it to log only messages
-from the ``security`` channel:
+from the ``security`` channel. You might add this in ``config.yml`` to log
+in all environments, or just ``config_prod.yml`` to happen only in ``prod``:
 
 .. configuration-block::