Document #399 in Release Notes

Author: marcphilipp

documentation/src/docs/asciidoc/release-notes-5.0.0-M3.adoc

@@ -112,6 +112,7 @@ on GitHub.
 * The `junit-platform-console` no longer has a mandatory dependency on
   https://pholser.github.io/jopt-simple/[JOpt Simple]. Thus, it's now possible to test custom
   code that uses a different version of that library.
+* Classpath scanning now supports JAR files.
 
 
 [[release-notes-5.0.0-m3-junit-jupiter]]