Add quick note about accessing config through session or item objects

Fix #5030

Author: nicoddemus

doc/en/deprecations.rst

@@ -60,7 +60,8 @@ If you still have concerns about this deprecation and future removal, please com
 
 The ``pytest.config`` global object is deprecated.  Instead use
 ``request.config`` (via the ``request`` fixture) or if you are a plugin author
-use the ``pytest_configure(config)`` hook.
+use the ``pytest_configure(config)`` hook. Note that many hooks can also access
+the ``config`` object indirectly, through ``session.config`` or ``item.config`` for example.
 
 .. _raises-warns-exec: