Support style/link optional parameters in createCustomElement to style wrapped React component.

### Expected Behaviour
In case of using Webpack Minicssextractplugin or StyleLoaderPlugin I want to be able to pass generated styles inside web component to style React component.

### Actual Behaviour
Right now only inline styles in React component will work behind shadow dom.

### Reproduce Scenario (including but not limited to)
#### Steps to Reproduce
Try to wrap React component with css modules.

#### Platform and Version
any

P.S. I could contribute code to add this functionality.

Start at the createCustomElement entry point mentioned in the issue and trace how the wrapped React component is placed behind the shadow DOM. Determine how optional style and link parameters should carry generated CSS from CSS modules, Webpack MiniCssExtractPlugin, or StyleLoaderPlugin into the component. Done means external generated styles can style the wrapped component, not only inline React styles.

Written by the indexing model from the issue text.