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/.gitignore b/.gitignore
index a7f8234..8cc2382 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: © 2021 Matthias Andreas Benkard <code@mail.matthias.benkard.de>
+#
+# SPDX-License-Identifier: LGPL-3.0-or-later
+
 /.gradle
 /.idea