message: Add doc to page..navigationTitle property
diff: @@ -27,6 +27,10 @@ export class PageModel extends PanelModelBase implements IPage {
  public get isPage() {
  return true;
  }
  + /**
  + * Use this property to show title in navigation buttons. If the value is empty then page name is used.
  + * @see survey.progressBarType
  + */
  public get navigationTitle(): string {
  return this.getLocalizableStringText("navigationTitle");
  }
  