Add mode indicator (LED) to Gazebo or RVIZ model

[Ryanf55]

User Story

As a NAV2 ArduPilot user, when I use the "Nav2 Goal" feature, if the drone is not armed, flying, and in guided mode, I can send a goal and it will not complete it. The UI does not show why.

Demo

Follow this process: https://github.com/ArduPilot/ardupilot_ros?tab=readme-ov-file#2-obstacle-avoidance-using-cartographer-and-nav2

Once RVIZ is running, use the "Nav2 Goal" button, and send a goal BEFORE you arm and launch the vehicle.

Ideas

Can we add a LED to the gazebo model that matches the ArduPilot AP_Notify/LED support? Then you can see if it's armed.