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.

从 issue 中提到的入口点 createCustomElement 开始，跟踪被包装的 React 组件如何被放置在 shadow DOM 后面。确定可选的 style 和 link 参数应如何将 CSS modules、Webpack MiniCssExtractPlugin 或 StyleLoaderPlugin 生成的 CSS 传递到组件中。当外部生成的样式能够为被包装的组件设置样式，而不仅仅是 inline React 样式时，即表示完成。

由索引模型根据 Issue 内容生成。