# Description

This PR extends the `ContactSensor` class to expose aggregated friction
forces for each filtered body. It uses the same vectorized approach used
for [`contact_points`](https://github.com/isaac-sim/IsaacLab/pull/2842).

Concretely, this change introduces:
- `ContactSensorCfg.track_friction_forces` toggle to turn on friction
tracking
- `ContactSensorData.friction_forces_w` where the sum of friction forces
for each filtered body are stored

Fixes https://github.com/isaac-sim/IsaacLab/issues/2074, #2064

## Performance

Results of `check_contact_sensor.py` with `track_friction_data = False`:
```
avg dt real-time 0.017448579105403043
avg dt real-time 0.017589360827958443
avg dt real-time 0.016146250123070787
```

Results of `check_contact_sensor.py` with `track_friction_data = True`:
```
avg dt real-time 0.01818224351439858
avg dt real-time 0.017720674386015163
avg dt real-time 0.01777262271923246
```

## Type of change
- New feature (non-breaking change which adds functionality)

## Checklist

- [x] I have read and understood the [contribution
guidelines](https://isaac-sim.github.io/IsaacLab/main/source/refs/contributing.html)
- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

---------
Signed-off-by: Kelly Guo <kellyg@nvidia.com>
Co-authored-by: Kelly Guo <kellyg@nvidia.com>