Import type PrismTheme

Hello, I just migrated to v2 and im wondering how to import the type PrismTheme. 

```javascript
import { PrismTheme } from "prism-react-renderer";
```

In v1.3.5 it was posible to use the import PrismTheme but currently im fasing the following error.

```
prism-react-renderer"' declares 'PrismTheme' locally, but it is not exported
```