Update What's New for 5.8

Author: Steve Riesenberg

docs/modules/ROOT/pages/whats-new.adoc

@@ -4,5 +4,7 @@
 Spring Security 5.8 provides a number of new features.
 Below are the highlights of the release.
 
+* https://github.com/spring-projects/spring-security/pull/11638[gh-11638] - Refresh remote JWK when unknown KID error occurs
 * https://github.com/spring-projects/spring-security/pull/11782[gh-11782] - @WithMockUser Supported as Merged Annotation
-	
+* https://github.com/spring-projects/spring-security/issues/11661[gh-11661] - Configurable authentication converter for resource-servers with token introspection
+* https://github.com/spring-projects/spring-security/pull/11771[gh-11771] - `HttpSecurityDsl` should support `apply` method