Update whatsnew.adoc

Author: fmbenhassine

spring-batch-docs/modules/ROOT/pages/whatsnew.adoc

@@ -13,6 +13,7 @@ Spring Batch 6.0 includes the following features and improvements:
 * xref:whatsnew.adoc#ability-to-recover-failed-job-executions[Ability to recover failed job executions]
 * xref:whatsnew.adoc#ability-to-stop-all-kind-of-steps[Ability to stop all kinds of steps]
 * xref:whatsnew.adoc#observability-with-jfr[Observability support with the Java Flight Recorder (JFR)]
+* xref:whatsnew.adoc#jspecify[Null safety annotations with JSpecify]
 * xref:whatsnew.adoc#deprecations-and-pruning[Deprecations and pruning]
 
 [[dependencies-upgrade]]
@@ -184,6 +185,11 @@ JFR is a powerful profiling and event collection framework built into the Java V
 
 This release introduces several JFR events to monitor key aspects of a batch job execution, including job and step executions, item reads and writes, as well as transaction boundaries.
 
+[[jspecify]]
+== Null safety annotations with JSpecify
+
+Spring Batch 6.0 APIs are now annotated with https://jspecify.dev/[JSpecify] annotations to provide better null-safety guarantees and improve code quality.
+
 [[deprecations-and-pruning]]
 == Deprecations and pruning