Change LICENSE to GPLv3 (#70)

* Change LICENSE file to GPLv3

* Change README LICENSE NOTICE to GPLv3

* Add NOTICE Header

app/src/main/res/xml/network_security_config.xml

@@ -1,4 +1,21 @@
 <?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ 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 GeneralPublic 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/>.
+  -->
 <network-security-config>
     <domain-config cleartextTrafficPermitted="true">
         <domain includeSubdomains="false">ehtracker.org</domain>