Add CacheStorage to public API

Author: aashishpatil-g

packages/firebase_data_connect/firebase_data_connect/lib/firebase_data_connect.dart

@@ -39,7 +39,4 @@ export 'src/optional.dart'
         listDeserializer,
         listSerializer;
 export 'src/timestamp.dart' show Timestamp;
-export 'src/cache/cache_data_types.dart' show CacheSettings, QueryFetchPolicy;
-//export 'src/cache/cache_manager.dart' show Cache;
-//export 'src/cache/cache_provider.dart' show CacheProvider;
-//export 'src/cache/sqlite_cache_provider.dart' show SQLite3CacheProvider;
+export 'src/cache/cache_data_types.dart' show CacheSettings, QueryFetchPolicy, CacheStorage;