readme update

README.md

@@ -27,7 +27,9 @@ C:\dev\ros2_humble\setup.ps1
 ```
 
 5. Build the modules. Use the following command from the main folder of this repo:   
-```colcon build --merge-install```
+```shell
+colcon build --merge-install
+```
 6. Launch all or single modules.
 
 ### Folder Structure (after building)