add copyright notice to DocumentComponent

src/DocumentComponent.ts

@@ -1,3 +1,19 @@
+/**
+ * Copyright © 2024 Cloudnode OÜ
+ *
+ * This file is part of @cldn/components.
+ *
+ * \@cldn/components is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser
+ * General Public License as published by the Free Software Foundation, either version 3 of the License,
+ * or (at your option) any later version.
+ *
+ * \@cldn/components is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the
+ * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License along with @cldn/components.
+ * If not, see <https://www.gnu.org/licenses/>.
+ */
 import {NodeComponent} from "./NodeComponent.js";
 
 /**