Add a note on how to seed the action space (#383)

gymnasium/core.py

@@ -45,6 +45,9 @@ class Env(Generic[ObsType, ActType]):
       ``super().reset(seed=seed)`` and when assessing ``self.np_random``.
 
     .. seealso:: For modifying or extending environments use the :py:class:`gymnasium.Wrapper` class
+
+    Note:
+        To get reproducible sampling of actions, a seed can be set with ``env.action_space.seed(123)``.
     """
 
     # Set this in SOME subclasses