shadow_hand.xml is adopted from https://github.com/isaac-sim/IsaacGymEnvs/tree/main/assets/mjcf/open_ai_assets.
LICENSE is copied from https://github.com/isaac-sim/IsaacGymEnvs/blob/main/assets/licenses/open_ai_assets-LICENSE.txt.
The modifications include combining the original robot.xml, shadow_hand.xml, shared_asset.xml, and shared.xml into a single, complete MJCF file, now named shadow_hand.xml. In this way, the MJCF could be loaded by MuJoCo.