Create semantic segmentation tutorial with robot.com's plugin

[pepisg]

Hi! At robot.com we recently open sourced https://github.com/kiwicampus/semantic_segmentation_layer. II set up https://github.com/pepisg/nav2_segmentation_demo to showcase its capabilities. As discussed with @SteveMacenski it could be cool to move the segmentation demo here

couple of questions:

1. My demo has a devcontainer, as for running the gazebo segmentation model i need onnx and pytorch. How should that be included here?
2. The seg layer, should that be a submodule in the tutorial?

[SteveMacenski]

1. Does it need the devcontainer? Not a bad option for those that want to use it, but as long as the Dockerfile can work standalone, that's good enough. I'd move the Dockerfile to the root of the package though.

The tutorials repo isn't packaged into binaries, so its OK to have more involved dependencies. Just make sure to have clear install instructions & hardware requirements listed.

https://github.com/pepisg/nav2_segmentation_demo/blob/main/rover/ros2/src/semantic_segmentation_node/config/ontology.yaml#L17 -- can this practically run on CPU (at some very low frame rate)?

With updates there: I see it runs Jazzy / Cyclone. Is Cyclone strictly required? If not, we should make this independent and let the users decide. Jazzy is good and we should keep that. But also have Rolling suppor for Lyrical and later.

2. I think the tutorial can tell people to clone it. For now, use your URL. If we submodule it and/or move it into navigation2.ai, then we should do there. But that's a small 'later' problem for the sake of the tutorial (just changing a URL). This would be no different if it were Nav2 itself.

[pepisg]

I just submitted a first draft at ros-navigation/docs.nav2.org#876, #136 . let me know what you think