ROS2 - Docker mod for code-server and openvscode-server

This mod adds ROS2 to code-server and openvscode-server, to be installed/updated during container start.

In code-server/openvscode-server docker arguments, set an environment variable DOCKER_MODS=linuxserver/mods:code-server-ros2

If adding multiple mods, enter them in an array separated by |, such as DOCKER_MODS=linuxserver/mods:code-server-ros2|linuxserver/mods:code-server-flutter

The current release ROS2 Humble and its development tools will be made available inside the container.