message: ChangeSummaries doc fix.
diff: Change Summaries are generated per changeset. Every generated Change Summary is therefore uniquely associated
  to the Changeset it was generated from.
  -iModelJs persists the generated Change Summaries in a local ECDb file called **Changes Cache File** next to the briefcase it belongs to.
  +iModelJs persists the generated Change Summaries in a local ECDb file called **Change Cache File** next to the briefcase it belongs to.
  > Change Summaries can only be generated from the iModelJs backend. See the [ChangeSummaryManager]($backend/ChangeSummaryManager) API for how to do it.
  