message: add missing changes observable export
diff: @@ -229,6 +229,7 @@ export * from "./Documents/Changes/DatabaseChange";
  export * from "./Documents/Changes/OperationStatusChange";
  export * from "./Documents/Changes/IDatabaseChanges";
  export * from "./Documents/Changes/IConnectableChanges";
  +export * from "./Documents/Changes/IChangesObservable";
  // HiLo
  export * from "./Documents/Identity/HiloIdGenerator";
  