create a direct tasks for mobile franka

[n7729697]

Description

This pull request adds a new direct task class for the Mobile Franka robot, enabling simplified control and evaluation of manipulation capabilities in a mobile setting. This allows direct instantiation and configuration without relying on intermediate wrappers or task composers.

Previously, no Mobile Franka tasks were implemented in marl setups. Environment Configuration:
Defined the MobileFrankaMARLCfg class inheriting from DirectMARLEnvCfg.
Configured the environment settings, including decimation, episode_length_s, possible_agents, action_spaces, and observation_spaces.

Simulation Settings:
Configured the simulation parameters using SimulationCfg, including:
Time step (dt=1/120).
Gravity ((0.0, 0.0, -9.81)).
Physics material properties (static_friction=1.0, dynamic_friction=1.0).
PhysX settings (e.g., bounce_threshold_velocity=0.2).

Robot Configuration:
Used MOBILE_FRANKA_CFG to define the mobile Franka robot configuration.
Set the initial state of the robot, including position, rotation, and joint positions.
Defined actuated joints (panda_joint1 to panda_joint7) and mobile base joints (dummy_base_prismatic_x_joint, dummy_base_prismatic_y_joint, etc.).

Goal Object Configuration:
Configured a goal object using VisualizationMarkersCfg with a red spherical marker to represent the goal.

Scene Configuration:
Defined the interactive scene using InteractiveSceneCfg with:
num_envs=512 for parallel environments.
env_spacing=3.0 for spacing between environments.
Enabled physics replication (replicate_physics=True).

Action and Observation Scaling:
Set action_scale=7.5 and dof_velocity_scale=0.1 to scale actions and velocities.
Limited the maximum base position to 3.0.

Reward Configuration:
Defined reward scales for various components:
Distance reward (dist_reward_scale=20).
Rotation reward (rot_reward_scale=0.5).
Finger distance reward (finger_dist_reward_scale=100.0).
Action penalty (action_penalty_scale=0.01), among others.

Reset Noise:
Configured reset noise parameters for position, DOF positions, and velocities, all set to 0.0 for deterministic resets.
These configurations collectively enable the MARL environment for the Mobile Franka robot, supporting multi-agent learning with distinct action and observation spaces for the robot arm (franka) and mobile base (base).

Fixes # (issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Screenshots

Please attach before and after screenshots of the change if applicable.

Checklist

• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there