#603: update readme with 6.0.0 release

Author: TheSnoozer

README.md

@@ -45,7 +45,7 @@ older version (4.x.x or older) are available via:
 
 Versions
 --------
-The current version is **5.0.0** ([changelist](https://github.com/git-commit-id/git-commit-id-maven-plugin/issues?q=milestone%3A5.0.0)).
+The current version is **6.0.0** ([changelist](https://github.com/git-commit-id/git-commit-id-maven-plugin/issues?q=milestone%3A6.0.0)).
 
 You can check the available versions by visiting [search.maven.org](https://search.maven.org/artifact/io.github.git-commit-id/git-commit-id-maven-plugin), though using the newest is obviously the best choice.
 
@@ -60,6 +60,7 @@ Here is an overview of the current plugin compatibility with Java
 | 3.0.0           | Java 1.8              |
 | 4.0.0           | Java 1.8              |
 | 5.0.0           | Java 11               |
+| 6.0.0           | Java 11               |
 
 
 Plugin compatibility with Maven