message: Improve _addMatrixClientListener docs
diff: @@ -81,8 +81,8 @@ export default {
  },
  /**
  - * Start listening to events emitted by matrixClient, dispatch an action created by the
  - * actionCreator function.
  + * Start listening to events of type eventName on matrixClient and when they are emitted,
  + * dispatch an action created by the actionCreator function.
  * @param {MatrixClient} matrixClient a MatrixClient to register a listener with.
  * @param {string} eventName the event to listen to on MatrixClient.
  * @param {function} actionCreator a function that should return an action to dispatch
  