Update readme.md

Author: dg

readme.md

@@ -1,5 +1,4 @@
-[Nette Tester](https://tester.nette.org): enjoyable unit testing
-================================================================
+[![Nette Tester](https://github.com/nette/tester/assets/194960/e841900b-2a8c-4f29-b93f-dfa4c80e2bb3)](https://tester.nette.org)
 
 [![Downloads this Month](https://img.shields.io/packagist/dm/nette/tester.svg)](https://packagist.org/packages/nette/tester)
 [![Tests](https://github.com/nette/tester/workflows/Tests/badge.svg?branch=master)](https://github.com/nette/tester/actions)