Added XArm7

[EdwardoSunny]

What this does

Added the UFactory XArm7 with gripper using files from mujoco-menagerie

Examples:

Title	Label
Adds xarm7 and xarm7 gripper	(✨ Feature)

How it was tested

Tested using the code inside of scripts/ to ensure compatibility with robosuite and functionality. If anyone wants to do further testing, simply select the robot as XArm7 and run program as usual.

How to checkout & try? (for the reviewer)

Any regular robosuite program, just replace robot with XArm7.

import numpy as np
import robosuite as suite

# create environment instance
env = suite.make(
    env_name="Lift", # try with other tasks like "Stack" and "Door"
    robots="XArm7",  # try with other robots like "Panda", "Sawyer", and "Jaco"
    has_renderer=True,
    has_offscreen_renderer=False,
    use_camera_obs=False,
)

# reset the environment
env.reset()

for i in range(1000):
    action = np.random.randn(*env.action_spec[0].shape) * 0.1
    obs, reward, done, info = env.step(action)  # take action in the environment
    env.render()  # render on display

@kevin-thankyou-lin @zhuyifengzju