Fix(types): Update Typescript definition file, declaring WebView class as a generic class (#1604)

Co-authored-by: iou90kant <dekang.liu@guokr.com>

index.d.ts

 
 export type WebViewProps = IOSWebViewProps & AndroidWebViewProps;
 
-declare class WebView extends Component<WebViewProps> {
+declare class WebView<P = {}> extends Component<WebViewProps & P> {
     /**
      * Go back one page in the webview's history.
      */