Set explicit autobackup rules

app/src/main/AndroidManifest.xml

@@ -14,6 +14,7 @@
     <application
         android:name=".App"
         android:allowBackup="true"
+        android:fullBackupContent="@xml/backup_rules"
         android:hardwareAccelerated="true"
         android:icon="@mipmap/ic_launcher"
         android:roundIcon="@mipmap/ic_launcher_round"

app/src/main/res/xml/backup_rules.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<full-backup-content>
+    <include domain="database" path="tachiyomi.db"/>
+</full-backup-content>