(improvement)(Headless) support semantic search in metric market (#934)

Co-authored-by: jolunoluo

headless/api/src/main/java/com/tencent/supersonic/headless/api/pojo/response/MetricResp.java

@@ -65,6 +65,8 @@ public class MetricResp extends SchemaItem {
 
     private Integer isPublish;
 
+    private double similarity;
+
     public void setClassifications(String tag) {
         if (StringUtils.isBlank(tag)) {
             classifications = Lists.newArrayList();