Add dummy javadoc to pkl-tools

pkl-tools/src/dummy/java/org/pkl/tools/Empty.java

@@ -0,0 +1,24 @@
+/**
+ * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed 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
+ *
+ *     https://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 CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.pkl.tools;
+
+/**
+ * This is an intentionally empty class.
+ */
+// TODO: figure out how to generate javadoc for a shadow jar.
+@SuppressWarnings("unused")
+public class Empty {
+}