stepping is advanced note

docs/Learning-Environment-Design.md

 #### Academy Pitfalls
 
 In some games, it may be desirable to step the environment with the Academy manually via `Academy.Instance.EnvironmentStep()`.
+Note, stepping manually is an advanced scenario and some care is required.
 If this is the case, be sure `Academy.Instance.EnvironmentStep()` is not called directly or indirectly by the agent's
 API e.g. from the `CollectObservations()`, `OnActionReceived`, and `Heuristic()` functions as this will
 cause an infinite loop that prevents the main Academy update function from being called.