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

[AndreyLuzinov]

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.

[alexmirea]

@AndreyLuzinov thank you for submitting this, contributions are of course welcome.