add missing export for FolderPicker

Author: joelfmrodrigues

src/index.ts

@@ -12,6 +12,7 @@ export * from './Progress';
 export * from './DateTimePicker';
 export * from './FilePicker';
 export * from './FolderExplorer';
+export * from './FolderPicker';
 export * from './IconPicker';
 
 export * from './IFrameDialog';