Add util to generate simulations yaml

[slinlee]

To integrate with the webapp UI and the features to select observations or reward terms and track/plot metrics, let's build that into pathmind-api.

It should include:

• observations
• metrics
• reward term
• The simulation class to execute
• action space description?
• single or multi-agent?

[maxpumperla]

at least we have the very basics already:

https://github.com/PathmindAI/pathmind-api/blob/main/pathmind/utils.py#L6

it's not difficult to pull off, we just need to agree on a suitable format. I can definitely make a suggestion.