[Feature Request] Dict Obs Spaces Support

[alexpalms]

🚀 Feature

As far as I understood by some preliminar tests, SBX currently does not support Dict observation spaces, do you have this feature in your roadmap? If yes when is it expected to be added?

Motivation

It would allow to extend the list of supported use cases featuring more complex/structured observation spaces

### Checklist

• [X] I have checked that there is no similar issue in the repo (required)