Adds reach task with IK controller

[louislelay]

📝 Description

This PR adds a reach task but instead of joint pos controller this time it's an ik controller. The task might look dumb as it is (we're trying to make him learned ik with an ik controller 🤣) but it will be useful as a first step toward lift task with an ik controller. Also, it still isn't perfect, my guess is that it should have a higher stiffness config.

Closes #48 & #11

Replaces #45

🛠 Type of Change

• New feature or enhancement

📷 Screenshots / Demos (if applicable)

rl-video-step-0.mp4

✅ Checklist

• I’ve run pre-commit on all modified files
• I’ve tested in simulation or verified that changes don’t break expected behavior
• I’ve updated documentation where needed
• I’ve reviewed open issues to ensure this is not a duplicate
• Code follows the repository’s style and structure