message: Add busy param to docs
diff: @@ -33,6 +33,8 @@ import MatrixClientPeg from '../../../MatrixClientPeg';
  * stageParams: params from the server for the stage being attempted
  * errorText: error message from a previous attempt to authenticate
  * submitAuthDict: a function which will be called with the new auth dict
  + * busy: a boolean indicating whether the auth logic is doing something
  + * the user needs to wait for.
  *
  * Each component may also provide the following functions (beyond the standard React ones):
  * focus: set the input focus appropriately in the form.
  