Support tele-op for Franka Kitchen environments ("vel" mode)

[sriramsk1999]

Changes Summary:

• Add ee_target to Franka Kitchen xml
• Fix bug in normalize_actions
• Handle teleop action for "vel" mode envs

Motivation:

Currently, the teleop code only supports "pos" mode environments, where the expected input action is the qpos coordinates. Other environments, like the Franka Kitchen envs, are "vel" mode - where input action is the velocity of each joint.

NOTE: Normalizing the qvel does not work, the values are too small and the end effector never reaches the teleop target. Is there some issue with how the normalization is called?

[vikashplus]

I haven't tested in cases you are using it now. This might be a good chance for me to test those. I'm traveling this week. I'll be able to take a look next week.

[sriramsk1999]

Bump on this PR. Even though the teleop works, it would be good to know if the implementation is correct, especially since it doesn't work when I normalize the velocities.

[vikashplus]

Let me know when its ready for a merge and I'll do a thorough review.

[sriramsk1999]

Ready for review!