[Proposal] Provide example usage for RslRlSymmetryCfg

[T-K-233]

Proposal

Provide a sample code to use the RslRlSymmetryCfg symmetry configuration in velocity task environments.

Motivation

In isaaclab_rl v0.1.2 release, the support for symmetry configurations for RSL-RL wrapper is added. However, it does not show how to utilize this feature in the training pipeline.

It would be great if we can add one or two locomotion velocity environments to demonstrate the usage of this feature.

Checklist

• I have checked that there is no similar issue in the repo (required)

[kellyguo11]

@ClemensSchwarke @Mayankm96 do we have any examples that we can share with the symmetry flag?