feat: Update copyright headers to all java files

Resolves #6 (closed)

src/main/java/org/eclipsefoundation/downloads/api/DrupalAPI.java

+/*
+ * Copyright (C) 2022 Eclipse Foundation.
+ * 
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ * 
+ * Author: Martin Lowe <martin.lowe@eclipse-foundation.org>
+ * 
+ * SPDX-License-Identifier: EPL-2.0
+*/
 package org.eclipsefoundation.downloads.api;
 
 import javax.ws.rs.GET;