add license header

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

app/src/main/res/drawable/reaction_self_background.xml

@@ -1,4 +1,22 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?><!--
+    Nextcloud Android client application
+
+    @author Marcel Hibbe
+    Copyright (C) 2022 Marcel Hibbe
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero 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 Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program. If not, see <http://www.gnu.org/licenses/>.
+-->
 <shape xmlns:android="http://schemas.android.com/apk/res/android" >
 
     <stroke