Lazy load images (#4228)

* Add lazy loading for many images
* Load sprites on first hover of scrubber

ui/v2.5/src/components/Scenes/SceneListTable.tsx

@@ -87,6 +87,7 @@ export const SceneListTable: React.FC<ISceneListTableProps> = (
         <td>
           <Link to={sceneLink}>
             <img
+              loading="lazy"
               className="image-thumbnail"
               alt={title}
               src={scene.paths.screenshot ?? ""}