Update README with visualization instructions

Added instructions for installing and using the Python viewer for visualizing recorded actions.

Author: loicmagne

README.md

@@ -12,6 +12,22 @@ Add the `Input Recording` source:
 
 That's it! Now every time you record, a `.parquet` file will be created with the same name as your recording, containing the state of your gamepad recorded at 500Hz. This will also work if you disconnect your gamepad midway, connect a new one etc.
 
+## Visualize recorded actions
+
+Install the Python viewer with
+```bash
+pip install -e python_viewer
+```
+
+Then use it with
+```bash
+irv <path/to/video_file.mp4> # this command will automatically look for the associated .parquet file
+irv <path/to/video_file.mp4> --path-parquet <path/to/annotations.parquet> # or explicitely provide the path to the parquet annotations 
+```
+
+You should see a [rerun](https://github.com/rerun-io/rerun) window like this one: 
+![image](https://github.com/user-attachments/assets/b8a9a280-b1fb-4076-a427-1c8dc0dc0bad)
+
 ## TODOs:
 - [ ] Support mouse/keyboard recordings
 - [ ] Add a GUI to select output format and input device to be recorded