Describe the bug

It looks like this file is missing these lines:

from .agibot import *
from .agility import *
from .cassie import *

I think this makes it more difficult for people to use the models from those files.

Steps to reproduce

from isaaclab_assets.robots import (
    CASSIE_CFG,
    AGIBOT_A2D_CFG,
    DIGIT_V4_CFG,
)

It produces this error

    from isaaclab_assets.robots import (
ImportError: cannot import name 'CASSIE_CFG' from 'isaaclab_assets.robots' (/home/user/IsaacLab/source/isaaclab_assets/isaaclab_assets/robots/__init__.py)

Checklist

• I have checked that there is no similar issue in the repo (required)
• I have checked that the issue is not in running Isaac Sim itself and is related to the repo

Acceptance Criteria

Add the criteria for which this task is considered done. If not known at issue creation time, you can add this once the issue is assigned.

• The relevant imports have been added