Add SPDX License information (#96)

Adding license information according to the SPDX stanard.
Used the reuse tool.
Bug: https://github.com/scsitape/stenc/issues/95

bash-completion/Makefile.am

@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: 2022 stenc authors
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
 if ENABLE_BASH_COMPLETION
 bashcompletiondir = $(BASH_COMPLETION_DIR)
 dist_bashcompletion_DATA = stenc

bash-completion/stenc

@@ -1,3 +1,8 @@
+#/usr/bin/env bash
+
+# SPDX-FileCopyrightText: 2022 stenc authors
+# SPDX-License-Identifier: GPL-2.0-or-later
+
 #stenc bash completion
 
 _stenc () {