Add usage to readme

README.md

@@ -25,3 +25,9 @@ cd ../.. # navigate to the catkin_ws directory
 catkin_make
 source devel/setup.zsh # if you use bash: source devel/setup.bash 
 ```
+# Usage
+## This planner can be chosen using the local_planner argument like so:
+```bash
+roslaunch arena_bringup start_arena.launch local_planner:=trail # Make sure that your virtual env/poetry is activated
+```
+## For more details regarding usage, please refer to our [documentation](https://arena-benchmark.readthedocs.io/en/latest/user_guides/usage/)