[feature request] Support for Parameterized Action Spaces in Stable-Baselines/SB3 Contrib

[NUrgell]

Hi!

I was wondering if there are any plans to support parameterized action spaces in Stable-Baselines or SB3 Contrib. Specifically, I'm referring to action spaces that combine discrete actions with associated continuous parameters—potentially represented using gym.spaces.Tuple or another approach, as described in this paper.

My main goal is to preserve the problem’s parameterized structure rather than discretizing a continuous space. Do you see a pathway for integrating such spaces into SB3?

I came across an earlier discussion on this topic in #100, but I haven't been able to find any recent updates. Is this still planned for version 3.1?

Thanks in advance! :)