added GPLv3 message

rhythmblock.lua

@@ -1,3 +1,19 @@
+-- Rhythmblock - music player for CC: Tweaked
+-- (c) 2021 mint <they@mint.lgbt>
+--
+-- 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 <https://www.gnu.org/licenses/>.
+
 -- Change these lines to change the GUI colors.
 accentColor = colors.gray 
 buttonColor = colors.lightGray