Add stable-baselines3

[R055A]

What is this Python project?

Stable Baselines 3 is a PyTorch version of Stable Baselines for reliable implementations of (deep) reinforcement learning algorithms.

What's the difference between this Python project and similar ones?

Stable Baselines 3 is a significant improvement from previous Stable Baseline versions providing:

• state-of-the-art PyTorch algorithms for (deep) reinforcement learning with
  • observation space and Tensorboard support
  • custom environments, policies, callbacks and interface
  • can integrate with other libraries
• a full list of features can be found using this link

Anyone who agrees with this pull request could submit an Approve review to it.

[Nick254lokolonyei]

@henriquebastos