Add kinova Link6

[anashoussaini]

Description

Added Kinova Link6 robot

Fixes:

Checklist

Please check off each item ([x]) once complete, or mark it as [N/A] if it doesn't apply:

• Added your name to CONTRIBUTORS.md (alphabetically by first name)
• Updated CHANGELOG.md:
  • Global changelog (if your change affects the overall repo)
  • Model-specific changelog (if it affects a specific model only)
• Followed the XML formatting/style guidelines (if editing MJCF)
• Ran pytest test/ locally and ensured all tests pass
• Signed the Contributor License Agreement (CLA)

Refer to the contributing guide if you're unsure about any of the steps.

[google-cla]

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View this failed invocation of the CLA check for more information.

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[louislelay]

Not sure the MuJoCo Menagerie maintainers will accept this PR if it comes from a private repository and isn’t officially recognized by the company. If you already have a working ROS package, maybe check with Kinova to see if they’d like to support it themselves and use yours as a base or inspiration?