[BUG] typing-extensions package not in pyproject.toml

[martins0n]

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Before submitting (must do checklist)

• Did you read the contribution guide?
• Did you update the docs? We use Numpy format for all the methods and classes.
• Did you write any new necessary tests?
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Type of Change

• Examples / docs / tutorials / contributors update
• Bug fix (non-breaking change which fixes an issue)
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Proposed Changes

Related Issue

Closing issues

closes #645

[github-actions]

🚀 Deployed on https://deploy-preview-656--etna-docs.netlify.app

[codecov-commenter]

Codecov Report

Merging #656 (1b464eb) into master (0f8efaf) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #656   +/-   ##
=======================================
  Coverage   84.45%   84.45%           
=======================================
  Files         119      119           
  Lines        6322     6322           
=======================================
  Hits         5339     5339           
  Misses        983      983           

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