Add a Google Play badge to the README

Author: alexbakker

README.md

@@ -7,6 +7,10 @@ __WebDAV Provider__ is an Android app that can expose WebDAV through Android's
 Storage Access Framework (SAF). This allows you to access your WebDAV storage
 through Android's built-in file explorer, as well as other apps on your device.
 
+[<img height=80 alt="Get it on Google Play"
+src="https://play.google.com/intl/en_us/badges/images/generic/en-play-badge.png"
+/>](https://play.google.com/store/apps/details?id=dev.rocli.android.webdav)
+
 ## Screenshots
 
 [<img src="screenshots/screenshot1.png"