fix(types): android/allowsFullscreenVideo (#590)

Fix missing `allowsFullscreenVideo` prop after https://github.com/react-native-community/react-native-webview/pull/325 got merged.

src/WebViewTypes.ts

    * @platform android
    */
   mixedContentMode?: 'never' | 'always' | 'compatibility';
+  
+  /**
+   * Sets ability to open fullscreen videos on Android devices.
+  */
+  allowsFullscreenVideo?: boolean;
 }
 
 export interface WebViewSharedProps extends ViewProps {