Update strings.xml

Author: luigimak

app/src/main/res/values/strings.xml

@@ -69,5 +69,7 @@
     <string name="backup_now">Backup Selected Partitions</string>
     <string name="vendor_boot_fmt">vendor_boot.img Format</string>
     <string name="active">Active</string>
+    <string name="unbootable">Unbootable</string>
+    <string name="successful">Successful</string>
     <!-- TODO: Make error and success messages string resources -->
-</resources>
+</resources>