Add forceCheck for react-lazyload

forceCheck is available to manually trigger checking for elements in viewport. Helpful when LazyLoad components enter the viewport without resize or scroll events, e.g. when the components' container was hidden then become visible.

types/react-lazyload/index.d.ts

@@ -24,3 +24,5 @@ export default class LazyLoad extends Component<LazyLoadProps> {
 }
 
 export  function lazyload(option: {}): LazyLoad;
+
+export function forceCheck(): void;