> type KeyType = string;

[NilsBaumgartner1994]

ERROR
22:05
./node_modules/sync-storage/src/index.js 5:5
Module parse failed: Unexpected token (5:5)
You may need an appropriate loader to handle this file type, currently no loaders are configured to process this file. See https://webpack.js.org/concepts#loaders
| import handleError from './helpers/handleError';
| 
> type KeyType = string;
| 
| class SyncStorage {