Dreamer-V2

[belerico]

Summary

This PR introduce the Dreamer-V2 algorithm from https://arxiv.org/abs/2010.02193

Type of Change

Please select the one relevant option below:

• New feature (non-breaking change that adds functionality)

Checklist

Please confirm that the following tasks have been completed:

• I have tested my changes locally and they work as expected. (Please describe the tests you performed.)
• I have added unit tests for my changes, or updated existing tests if necessary.
• I have updated the documentation, if applicable.
• I have installed pre-commit and run locally for my code changes.

Screenshots or Visuals (Optional)

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Additional Information (Optional)

Those are the training loss and rewards con DMC Walker-Walk with the standard hyperparameters found in dreamer_v2/args.py

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[belerico]

Maybe it's better to account for the action repeat as we have done in Dreamer-V1 @michele-milesi