Adds Shadow Hand environment with vision and proprioception
observations. Image observations are used to train a CNN with RGB,
depth, and segmentation images, regressing on keypoint states that are
then combined with proprioception observations to be fed into an
asymmetric actor-critic policy.

- New feature (non-breaking change which adds functionality)
- This change requires a documentation update

![image](https://github.com/user-attachments/assets/d67c966b-2931-4ee4-84d1-8bc004471a21)

- [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
- [ ] 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
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