Add release notes link for 4.2.4

Author: plamentotev

README.md

@@ -18,6 +18,7 @@ This patch has been integrated into the Release 3.6.0
 
 You can find details about the different releases in the [Release Notes](https://github.com/codehaus-plexus/plexus-archiver/blob/master/ReleaseNotes.md).
 
+ * [Release 4.2.4](https://github.com/codehaus-plexus/plexus-archiver/releases/tag/plexus-archiver-4.2.4).
  * [Release 4.2.3](https://github.com/codehaus-plexus/plexus-archiver/releases/tag/plexus-archiver-4.2.3).
  * [Release 4.2.2](https://github.com/codehaus-plexus/plexus-archiver/releases/tag/plexus-archiver-4.2.2).
  * [Release 4.2.1](https://github.com/codehaus-plexus/plexus-archiver/blob/master/ReleaseNotes.md#plexus-archiver-421).