message: 2313: Add docstring for `Step` event.
diff: @@ -112,6 +112,7 @@ pub enum SseData {
  },
  /// New finality signature received.
  FinalitySignature(Box<FinalitySignature>),
  + /// The execution effects produced by a `StepRequest`.
  Step {
  era_id: EraId,
  #[data_size(skip)]
  