Add icon for 3.x.

Related: #1171.

Author: gregturn

README.adoc

@@ -2,6 +2,7 @@ image:https://spring.io/badges/spring-ws/ga.svg["Spring Web Services", link="htt
 image:https://spring.io/badges/spring-ws/snapshot.svg["Spring Web Services", link="https://spring.io/projects/spring-ws#learn"]
 
 image:https://jenkins.spring.io/buildStatus/icon?job=spring-ws%2Fmaster&subject=master[link=https://jenkins.spring.io/view/SpringWebServices/job/spring-ws/]
+image:https://jenkins.spring.io/buildStatus/icon?job=spring-ws%2F3.x&subject=master[link=https://jenkins.spring.io/view/SpringWebServices/job/spring-ws/]
 image:https://jenkins.spring.io/buildStatus/icon?job=spring-ws%2F2.x&subject=2.x[link=https://jenkins.spring.io/view/SpringWebServices/job/spring-ws/]
 
 = Spring Web Services