Change LICENSE to GPLv3 (#70)

* Change LICENSE file to GPLv3

* Change README LICENSE NOTICE to GPLv3

* Add NOTICE Header

app/src/main/java/com/hippo/ehviewer/WindowInsetsAnimationHelper.java

@@ -1,3 +1,21 @@
+/*
+ * Copyright 2022 Tarsin Norbin
+ *
+ * This file is part of EhViewer
+ *
+ * EhViewer 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.
+ *
+ * EhViewer 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 EhViewer.
+ * If not, see <https://www.gnu.org/licenses/>.
+ */
+
 package com.hippo.ehviewer;
 
 import android.view.View;