Provide Docker image with the necessary backend

For someone using BlueOS, it's easy to connect to the vehicle as no additional tools are required, but for those without BlueOS, that are running all the backend providers in their own machine, there are [a lot of steps to get up and running](https://github.com/bluerobotics/cockpit/pull/588).

It would be really good for the project if we could have a Docker image with all the necessary tools (mavlink-router/mavp2p, mavlink2rest and mavlink-camera-manager) included.

A nice bonus would be if it had a SITL instance already connected, for those without a flight-controller.

Solving this issue would really help the project, as it's the main entrance barrier today for someone that wants to start contributing to Cockpit.

Start with the setup steps described in pull request #588 and compare how mavlink-router/mavp2p, mavlink2rest, and mavlink-camera-manager are currently run. Define the Docker image's included providers and document how to verify the non-BlueOS setup; treat the SITL connection as an optional bonus.

Written by the indexing model from the issue text.