Add license header to ergodox_extended.c

keyboards/ergodox_extended/ergodox_extended.c

@@ -1,3 +1,21 @@
+/*
+Copyright 2020 Marcus Young <myoung34@my.apsu.edu>
+Copyright 2024 Adam Coleman <gephorian@gmail.com>
+
+This program 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 2 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
 #include "quantum.h"
 
 #ifdef SWAP_HANDS_ENABLE