Clarify licensing through REUSE annotations.

 - Manual: GFDL-1.3-or-later
 - Library: LGPL-3.0-or-later
 - Examples: GPL-3.0-or-later

Change-Id: Ia9637209724b416a157edc2027a0faa7ca9d5c25
diff --git a/core/pom.xml b/core/pom.xml
index eed69aa..419e4b2 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -1,4 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
+
+<!--
+SPDX-FileCopyrightText: © 2021 Matthias Andreas Benkard <code@mail.matthias.benkard.de>
+
+SPDX-License-Identifier: LGPL-3.0-or-later
+-->
+
 <project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">