return render frames from gymnasium render function

[m-m-adams]

The gymnasium render function returns frames in RGB array mode. This commit just passes through the return of the gymnasium render

This is useful for saving animations for demonstrations

[Toni-SM]

Hi @m-m-adams

Can you please make a clean pull request only with the change to return the values depending on the selected display mode. There are many changes in the file related to formatting / code style that are not related to the implemented feature.

[Toni-SM]

Hi @m-m-adams

Due to the features introduced in what will be version 1.0.0-preview.1 there are the following elements:

• The gymnasium wrapper is now in a separate file, and there are two wrappers (one for PyTorch and one for JAX).
• All changes must be made on the develop branch or another branch (except main). The main branch will only be updated from develop.

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Then, to also cover the gymnasium wrapper for JAX, please, open a new pull-request on the develop branch and update the following files:

• https://github.com/Toni-SM/skrl/blob/develop/skrl/envs/torch/wrappers/gymnasium_envs.py
• https://github.com/Toni-SM/skrl/blob/develop/skrl/envs/jax/wrappers/gymnasium_envs.py

Also, please, follow the commit convention described in CONTRIBUTING.md (in particular the first subpoint):

https://github.com/Toni-SM/skrl/blob/6b8b70fc2f5fd13087c70a9b51f0ef630c638bcc/CONTRIBUTING.md?plain=1#L48-L51

I am going to close this pull request Waiting for the new pull-request... :)