docs: add Docker section to the readme

Author: khaledmohamed00

README.md

@@ -20,6 +20,32 @@ pip config --site set global.no-build-isolation false
 pip install -ve .
 ```
 
+## Docker (GUI + GPU + HW add-ons)
+
+**Prereqs:** Docker + docker-compose, X11 on host, NVIDIA driver + NVIDIA Container Toolkit (legacy `runtime: nvidia`).  
+**Layout:** `Docker/Dockerfile`, overrides in `compose/` (`base.yml`, `gui.yml`, `gpu.yml`, `hw.yml`).
+
+### Build the image
+`docker-compose -f compose/base.yml build dev`
+
+### (GUI) allow X access (host)
+`export XAUTHORITY=${XAUTHORITY:-$HOME/.Xauthority}`  
+`xhost +si:localuser:root`
+
+### Run container with GUI + GPU + HW and open a shell
+`docker-compose -f compose/base.yml -f compose/gui.yml -f compose/gpu.yml -f compose/hw.yml run --rm run bash`  
+*(Use fewer `-f` files for lighter setups, e.g., GUI+GPU without HW.)*
+
+### Inside the container
+`pip install -v -e extensions/rcs_fr3`  
+`cd examples`  
+`python fr3_env_cartesian_control.py`
+
+### Troubleshooting
+- **`nvidia-smi` missing in container:** ensure it exists on host at `/usr/bin/nvidia-smi` (GPU override bind-mounts it).  
+- **GUI can’t open:** re-run the `xhost` command and confirm `$DISPLAY` is set on the host.  
+
+
 ## Usage
 The python package is called `rcs`.