Add (quantum) relative_entropy to quantum_info.entropies

[renatomello]

Checklist:

• Reviewers confirm new code works as expected.
• Tests are passing.
• Coverage does not decrease.
• Documentation is updated.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (75ec076) 100.00% compared to head (8cc2ade) 100.00%.
Report is 1 commits behind head on entanglement_entropy.

Additional details and impacted files

@@                  Coverage Diff                   @@
##           entanglement_entropy     #1177   +/-   ##
======================================================
  Coverage                100.00%   100.00%           
======================================================
  Files                        70        70           
  Lines                      9906      9938   +32     
======================================================
+ Hits                       9906      9938   +32     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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