Add link to User Guide for new org.junit.start module

Author: sormuras

documentation/src/docs/asciidoc/release-notes/release-notes-6.1.0-M1.adoc

@@ -49,7 +49,8 @@ repository on GitHub.
 ==== New Features and Improvements
 
 * Introduce new module `org.junit.start` for writing and running tests. It simplifies
-  using JUnit in compact source files together with a single module import statement:
+  using JUnit in compact source files together with a single `module import` statement.
+  Find an example at the <<../user-guide/#running-tests-source-launcher, User Guide>>.
 * Introduce new `dynamicTest(Consumer<? super Configuration>)` factory method for dynamic
   tests. It allows configuring the `ExecutionMode` of the dynamic test in addition to its
   display name, test source URI, and executable.