feat: 机器人列表上方添加 Add 按钮

Author: liuweiGL

src/main/resources/io/jenkins/plugins/DingTalkGlobalConfig/config.jelly

@@ -45,6 +45,7 @@
       <j:set var="robotConfigDescriptor"
         value="${descriptor.getDingTalkRobotConfigDescriptor()}"/>
       <f:repeatable
+        enableTopButton="true"
         field="robotConfigs"
         var="item"
         items="robotConfigs">