[Feature Request] Support for multi input policies in CrossQ

[RaikoPipe]

🚀 Feature

Support for multi input policies in CrossQ.

Motivation

The newly implemented CrossQ algorithm doesn't currently support MultiInputPolicy. The algorithm seems promising and I would like to use it for my own custom env, which is a dict env requiring multi input policy support.

Pitch

I implemented the feature in pull request #268. It's a work in progress but might be useful to those who require the feature until an official update is rolled out.

Alternatives

A current alternative lies in switching to the jax version of stable-baselines3 (https://github.com/araffin/sbx), which has minimal support for the feature.

Additional context

No response

Checklist

• [X] I have checked that there is no similar issue in the repo
• [X] If I'm requesting a new feature, I have proposed alternatives

[araffin]

Hello, thanks for the proposal, what is missing currently? where would you need some help?