Improve readme and badges (#955)

* Update README.md

* Update badges

README.md

@@ -1,25 +1,30 @@
-Transportr
-==========
+Transportr | [![Build and test](https://github.com/grote/Transportr/actions/workflows/build.yml/badge.svg)](https://github.com/grote/Transportr/actions/workflows/build.yml)
+============================================================================================================================================================================
 
 The public transport companion that respects your privacy and your freedom.
 Transportr is a non-profit app developed by people around the world to make using public transport as easy as possible wherever you are. 
 
 [![Transportr Logo](./app/src/main/res/mipmap-xhdpi/ic_launcher.png)](https://transportr.app)
-[![Build and test](https://github.com/grote/Transportr/actions/workflows/build.yml/badge.svg)](https://github.com/grote/Transportr/actions/workflows/build.yml)
 
 Please **[visit the website](https://transportr.app)** for more information!
 
 If you find any issues with this app, please report them at [the issue tracker](https://github.com/grote/Transportr/issues). Contributions are both encouraged and appreciated. If you like to contribute please [check the website](https://transportr.app/contribute) for more information.
 
-The upstream repository is at: https://github.com/grote/Transportr
-
 [![Follow @TransportrApp](artwork/twitter.png)](https://twitter.com/TransportrApp)
 
 Get Transportr
 --------------
 
-[![Available on F-Droid](./artwork/f-droid.png)](https://f-droid.org/repository/browse/?fdid=de.grobox.liberario)
-[![Available on Google Play](./artwork/google-play.png)](https://play.google.com/store/apps/details?id=de.grobox.liberario)
+<a href="https://f-droid.org/packages/de.grobox.liberario">
+    <img src="./artwork/f-droid.png"
+    alt="Get it on F-Droid"
+    height="80">
+</a>
+<a href="https://play.google.com/store/apps/details?id=de.grobox.liberario">
+    <img src="./artwork/google-play.png"
+    alt="Get it on Google Play"
+    height="80"/>
+</a>
 
 Pre-releases and beta versions for advanced users are available via [a special F-Droid repository](http://grobox.de/fdroid/).