optimize: add Grafana dashboard JSON for NamingServer metrics (#8002)

Author: contrueCT

changes/en-us/2.x.md

@@ -24,7 +24,7 @@ Add changes here for all PR submitted to the 2.x branch.
 - [[#7000](https://github.com/apache/incubator-seata/pull/7000)] support multi-version codec & fix not returning client registration failure msg.
 - [[#7865](https://github.com/apache/incubator-seata/pull/7865)] add Benchmark CLI tool
 - [[#7903](https://github.com/apache/incubator-seata/pull/7903)] Support HTTP/2 stream push for the Watch API in Server Raft mode
-
+- [[#8002](https://github.com/apache/incubator-seata/pull/8002)] add Grafana dashboard JSON for NamingServer metrics
 
 ### bugfix:
 

changes/zh-cn/2.x.md

@@ -25,6 +25,7 @@
 - [[#7000](https://github.com/apache/incubator-seata/pull/7000)] 支持多版本codec，修复不返回客户端注册失败消息的问题
 - [[#7865](https://github.com/apache/incubator-seata/pull/7865)] 新增 Benchmark 命令行工具
 - [[#7903](https://github.com/apache/incubator-seata/pull/7903)] 在Server Raft模式下支持Watch API的HTTP/2流推送
+- [[#8002](https://github.com/apache/incubator-seata/pull/8002)] 为namingserver指标增加Grafana dashboard JSON
 
 ### bugfix: