Add example usage of RslRlSymmetryCfg in velocity environment

[T-K-233]

//Before Merge//

I would like to know if this is the proper way to implement this functionality. Please let me know if there are better ways to structure the code.

Description

This PR creates SymmetryCfg and SymmetryTermCfg config classes that can be used to set symmetric configuration to the RSL-RL framework. An example data augmentation function, symmetry_data_augmentation_function, is also provided to implement corresponding symmetry terms.

This PR answers Issue #2835.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Screenshots

Please attach before and after screenshots of the change if applicable.

Checklist

• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[kellyguo11]

Thanks for the PR! We will work on putting out an example setup with symmetry soon.

[T-K-233]

Sounds good! Please let me know if I can help on anything

[Mayankm96]

@T-K-233 I merged the symmetry MR with examples for multiple environments. Please feel free to adapt this MR to that. Let us know if you have questions.