Update README.md

README.md

@@ -7,6 +7,15 @@ graph TD;
     
 ```    
 
+
+```mermaid
+graph TD;
+    B-->D;
+    C-->D;
+    
+``` 
+
+
 ```mermaid
 erDiagram;
     t_client_user  ||--o{ t_client_user_device : has;