Upkie-locomotion

Added

- Environment: ``UpkieServosEnv-v1``
- PPO balancer: distribute sample policy
- Pink balancer: ``--visualize`` argument
- Spine: Air Bullet, same as Bullet but floating in the air
- Utils: Pinocchio utility functions

Changed

- Load description from local package rather than cloning a repository
- Rename ``UpkieWheelsReward`` to ``StandingReward``

Fixed

- UpkieWheelsEnv: observation limits for ground position and velocity
- Pink balancer: reduce LM damping to fix stalling when crouching
- PPO balancer: get environment id (thanks Varun-GP)

Added

- UpkieWheelsEnv: return action and observation dicts in ``info``

Added

- Add ``upkie_locomotion.envs.register`` function
- PPO balancer: setting for total number of training timesteps
- UpkieWheelsEnv: simple example

Changed

- UpkieWheelsEnv: remove dependency on gin

Added

- Agent: PPO balancer
- Environment: ``UpkieWheelsEnv-v1``
- Observers: Base pitch

Changed

- Promote ``utils.imu`` to a proper Python observer
- Switch from ``aiorate`` to ``loop_rate_limiters``

Fixed

- Document both C++ and Python code with Doxygen
- Python requirements and dependencies in Bazel

Starting this changelog.