add copyright to logging

cyberwow/lib/logging.dart

@@ -1,3 +1,24 @@
+/*
+
+Copyright 2019 fuwa
+
+This file is part of CyberWOW.
+
+CyberWOW 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.
+
+CyberWOW 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 CyberWOW.  If not, see <https://www.gnu.org/licenses/>.
+
+*/
+
 import 'package:logging/logging.dart';
 
 final Logger log = Logger('Default');