readme: info about supported versions

Author: dg

readme.md

@@ -31,10 +31,13 @@ composer require nette/tester --dev
 
 Alternatively, you can download the [tester.phar](https://github.com/nette/tester/releases) file.
 
-Nette Tester 2.0 requires PHP 5.6 and supports PHP up to 7.3. The 2.1 version and newer require PHP 7.1.
+Nette Tester 2.3 requires PHP 7.1 and supports PHP up to 7.4.
+Nette Tester 2.1 and 2.2 requires PHP 7.1 and supports PHP up to 7.3.
+Nette Tester 2.0 requires PHP 5.6 and supports PHP up to 7.3.
 Collecting and processing code coverage information depends on Xdebug or PCOV extension, or PHPDBG SAPI.
 
 
+
 Writing Tests
 -------------