Merge pull request SecUSo#28 from jahway603/documentation

documentation: Added info re: Privacy Friendly Backup to resolve Issue SecUSo#27

README.md

@@ -35,6 +35,10 @@ For more information about the app and how it works, please take a look at the W
 Mininum SDK: 21
 Target SDK: 33
 
+## Data Backup
+
+You can use the [Privacy Friendly Backup app](https://github.com/SecUSo/privacy-friendly-backup) to backup and restore this application's data. This can also be used to migrate your data to a new phone.
+
 ## Translation
 
 If you want to help translate this app, you can use [Weblate](https://hosted.weblate.org/projects/privacy-friendly-2048/).