[feature] add SKRL example

[edbeeching]

The skrl lib looks interesting, particularly as they just added multi-agent support. It would be good to add support and an example.

https://skrl.readthedocs.io/en/latest/

[Ivan-267]

Sounds interesting, especially the multi-agent support. Might need some plugin and env modifications to differentiate the different agent types, and if making an example using MAPPO, some suitable/cooperative task idea.

[Ivan-267]

pycharm64_X5uc3IamGA.mp4

Sharing a small test case from yesterday based on the examples from SKRL.
It's PPO with num_agents set to 1 and only one observation space used, not a proper/full implementation by any means nor a test of the learning performance, just a first attempt to get the framework to start training with Godot-RL environment.

For a full implementation with multi-agents with separate policies, observations, etc., more changes are needed.

[edbeeching]

Cool. It seems their MARL support is quite limited at the moment. Perhaps we can focus on other things until they have better support?

[Ivan-267]

Sure, we could work on a potential more complete implementation at any point. Just asking since I'm not that familiar with any MARL implementation yet and not sure what to expect, are there some useful features that are not supported yet?

Regarding the support on our side, I was only just starting to consider what might be needed.
Assigning a name for each AIController and then in sync.gd having a dictionary with all unique names as keys and all agent instances with that name as values is about as far as I got on the Godot side, but whether that's a good approach and the other details could be considered more when/if we start working on a more proper implementation.