Feat: add algo aurora

[felixchalumeau]

Related issues: #142

This PR introduces AURORA and PGA-AURORA, algorithms that define the behaviour descriptor in an unsupervised manner.

This PR introduces:

• unstructured repertoire
• aurora class
• utils to define an auto encoder with lstm
• test for aurora
• example for aurora and pga aurora
• updated readme and docs

Checks

• a clear description of the PR has been added
• sufficient tests have been written
• relevant section added to the documentation
• example notebook added to the repo
• clean docstrings and comments have been written
• if any issue/observation has been discovered, a new issue has been opened

Future improvements

We are pushing this PR to have the code open sourced for ICLR but some part of the code do not reach the code quality standard that we have been fixing for QDax until now. I will open an issue: we will need to clean this in the near future.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 92.87305% with 32 lines in your changes missing coverage. Please review.

Project coverage is 92.30%. Comparing base (b221c68) to head (6c5801e).
Report is 15 commits behind head on develop.

Files with missing lines	Patch %	Lines
qdax/core/containers/unstructured_repertoire.py	83.47%	19 Missing ⚠️
tests/core_test/aurora_test.py	90.32%	9 Missing ⚠️
qdax/utils/train_seq2seq.py	95.58%	3 Missing ⚠️
...x/core/neuroevolution/networks/seq2seq_networks.py	98.59%	1 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #144      +/-   ##
===========================================
+ Coverage    92.28%   92.30%   +0.01%     
===========================================
  Files          120      125       +5     
  Lines         7055     7485     +430     
===========================================
+ Hits          6511     6909     +398     
- Misses         544      576      +32     

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[Lookatator]

@felixchalumeau, do you have any comment regarding all the refactoring that has been done? 😄

[felixchalumeau]

Happy with it!