Add self-updater for github builds

mastodon/src/main/res/drawable/update_progress.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+	<item android:id="@android:id/progress">
+		<shape
+			android:innerRadius="16dp"
+			android:shape="ring"
+			android:thickness="4dp"
+			android:useLevel="true">
+			<solid android:color="?colorSearchHint"/>
+		</shape>
+	</item>
+</layer-list>