Add LICENCE

ConfigParser.cs

+// i3csstatus - Alternative generator of i3 status bar written in c#
+// (c)   2022 Jiri Kalvoda <jirikalvoda@kam.mff.cuni.cz>
+
+// 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
+// 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/>.
+
 #nullable enable
 using System;
 using System.Collections.Generic;

Module.cs

+// i3csstatus - Alternative generator of i3 status bar written in c#
+// (c)   2022 Jiri Kalvoda <jirikalvoda@kam.mff.cuni.cz>
+
+// 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
+// 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/>.
+
 using System;
 using System.Collections.Generic;
 using System.Text;

Parsers.cs

+// i3csstatus - Alternative generator of i3 status bar written in c#
+// (c)   2022 Jiri Kalvoda <jirikalvoda@kam.mff.cuni.cz>
+
+// 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
+// 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/>.
+
 #nullable enable
 using System;
 using System.Collections.Generic;

Program.cs

-#nullable enable
+// i3csstatus - Alternative generator of i3 status bar written in c#
+// (c)   2022 Jiri Kalvoda <jirikalvoda@kam.mff.cuni.cz>
+
+// 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
+// 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/>.
+
+#nullable enable
 using System;
 using System.Collections.Generic;
 using System.Text;