Update README.md

README.md

@@ -3,7 +3,7 @@
 
 
 OpenXG-UDR Arch
-
+```
 ├── build:         Build directory, contains targets and object files generated by compilation of network functions. 
     ├── scripts:   Directory containing scripts for building network functions.
     ├── ext:       Directory containing spdlog and pistache and the JSON library.
@@ -15,6 +15,7 @@ OpenXG-UDR Arch
     ├── model:     UDR service. 
     ├── api:       UDR service.
     └── impl:      UDR service.
+```
     
 ## Download source code from Gitlab
 ```