fix: add missing s2 theme file for thumbnail

components/thumbnail/themes/spectrum-two.css

@@ -0,0 +1,18 @@
+/*!
+ * Copyright 2024 Adobe. All rights reserved.
+ *
+ * This file is licensed to you under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License. You may obtain a copy
+ * of the License at <http://www.apache.org/licenses/LICENSE-2.0>
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under
+ * the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
+ * OF ANY KIND, either express or implied. See the License for the specific language
+ * governing permissions and limitations under the License.
+ */
+
+@container style(--system: spectrum) {
+	.spectrum-Thumbnail {
+		--spectrum-thumbnail-border-radius: 2px;
+	}
+}