Skeleton component: fix warning about key prop (https://github.com/woocommerce/woocommerce-blocks/pull/9018)

plugins/woocommerce-blocks/assets/js/base/components/skeleton/index.tsx

@@ -10,11 +10,15 @@ export interface SkeletonProps {
 export const Skeleton = ( {
 	numberOfLines = 1,
 }: SkeletonProps ): JSX.Element => {
-	const skeletonLines = Array( numberOfLines ).fill(
+	const skeletonLines = Array.from(
+		{ length: numberOfLines },
+		( _: undefined, index ) => (
 			<span
 				className="wc-block-components-skeleton-text-line"
 				aria-hidden="true"
+				key={ index }
 			/>
+		)
 	);
 	return (
 		<div className="wc-block-components-skeleton">{ skeletonLines }</div>