Link release APK in readme

Author: cubei

Diff for: README.md

@@ -4,3 +4,5 @@ Simple flash card android app with csv files as input.
 The app is meant for stuff like learning vocabulary of different languages.
 
 Play Store: https://play.google.com/store/apps/details?id=com.quchen.flashcard
+
+[Or latest APK from repo](app/release/app-release.apk)