Clarifies license to prevent dispute

src/main/java/net/knarcraft/permissionsigns/PermissionSigns.java

@@ -34,6 +34,26 @@ import java.util.Queue;
 import java.util.UUID;
 import java.util.stream.Stream;
 
+/*
+PermissionSigns - A permission shop plugin for Spigot
+Copyright (C) 2022 Kristian Knarvik (EpicKnarvik97)
+
+The following license notice applies to all source and resource files in the PermissionSigns project:
+
+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 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
 /**
  * The main permissionsigns class
  */