doc: add data model diagram in concept page

docs/en/04-concept/index.md

@@ -158,7 +158,7 @@ Queries can be executed on both a table (subtable) and a STable. For a query on
 
 In TDengine, it is recommended to use a subtable instead of a regular table for a DCP. In the meters example, we can create subtables like d1001, d1002, d1003, and d1004 under super table meters.
 
-To better understand the data model using super table and subtable, please refer to [Meters Data Model Diagram](supertable.webp)
+To better understand the data model using super table and subtable, please refer to ![Meters Data Model Diagram](./supertable.webp)
 
 ## Database
 

docs/zh/04-concept/index.md

@@ -159,7 +159,7 @@ TDengine 建议用数据采集点的名字（如上表中的 D1001）来做表
 
 TDengine系统建议给一个数据采集点建表，需要通过超级表建表，而不是建普通表。在智能电表的示例中，我们可以通过超级表meters创建子表d1001, d1002, d1003, d1004等。
 
-为了更好地理解超级与子表的关系，可以参考 [智能电表数据模型示意图](supertable.webp)
+为了更好地理解超级与子表的关系，可以参考 ![智能电表数据模型示意图](./supertable.webp)
 
 ## 库 (database)