__apt_unattended_upgrades: add license header

cdist/conf/type/__apt_unattended_upgrades/manifest

@@ -1,4 +1,22 @@
 #!/bin/sh -e
+#
+# 2020 Ander Punnar (ander-at-kvlt-dot-ee)
+#
+# This file is part of cdist.
+#
+# cdist is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# cdist 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with cdist. If not, see <http://www.gnu.org/licenses/>.
+#
 
 __package unattended-upgrades