Add a short Readme for the Demo (in case it's opened as top-level dir…

… in an IDE)

demo/README.md

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+# Arbitration Graphs Demo and Tutorial
+
+This is a demo of the [arbitration_graphs](https://github.com/KIT-MRT/arbitration_graphs) library using Pac-Man as an example application.  
+The arbitration graph controls Pac-Man on its journey to collect tasty dots 🍬
+
+Run the demo with:
+
+```bash
+git clone https://github.com/KIT-MRT/arbitration_graphs.git
+cd arbitration_graphs/demo
+docker compose up
+```
+
+Open the GUI with your favorite browser:  
+[http://0.0.0.0:8080](http://0.0.0.0:8080)
+
+
+## Tutorial
+
+If you're here for the tutorial, follow the instructions on our [Tutorial GitHub Page](https://kit-mrt.github.io/arbitration_graphs/docs/Tutorial.md).