Problem using webpack with fileSync Appender

Hello. I am experiencing the same issue as reported in https://github.com/log4js-node/log4js-node/issues/816 when using the FileSync appender and Webpack.

```
The "path" argument must be of type string. Received type undefined.
```

Could it be that it requires the same solution of adding it to coreAppenders in appenders/index.js ?
