Update LICENSE

LICENSE

@@ -672,3 +672,24 @@ may consider it more useful to permit linking proprietary applications with
 the library.  If this is what you want to do, use the GNU Lesser General
 Public License instead of this License.  But first, please read
 <https://www.gnu.org/licenses/why-not-lgpl.html>.
+
+
+This file is part of TetraX.
+
+TetraX micromagnetic package
+Copyright (C) 2021 Attila Kákay, Lukas Körber
+Contributions by Gwendolyn Quasebarth, Alexander Hempel, Friedrich Zahn, Riccardo Hertel.
+
+TetraX 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.
+
+This program 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 TetraX.  If not, see <http://www.gnu.org/licenses/>.
+