Migrate to pixi

[kklein]

I think that we should add a 'development' section in the docs as a follow-up to this PR; explaining how one can locally

• install the environment
• install and run pre-commit hooks and
• run the tests

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.67%. Comparing base (390d53c) to head (5ee2860).
Report is 56 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #12   +/-   ##
=======================================
  Coverage   94.67%   94.67%           
=======================================
  Files          14       14           
  Lines        1295     1295           
=======================================
  Hits         1226     1226           
  Misses         69       69           

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[kklein]

FYI @DelongChenQC, @MatthiasLoefflerQC (couldn't find Arsenyi's GitHub handle)

[pavelzw]

When properly checking it in pre-commit (see other comment), we don't need this here as it's already being checked by the pre-commit hook.

[kklein]

Removed it!

[FrancescMartiEscofetQC]

Looking good, I think it's important to add in the README how one can build the environment and the basics for development but maybe we can leave it for another PR.

[kklein]

The Windows tests are failing - I created an issue to follow up on it after this PR:
#24

[FrancescMartiEscofetQC]

LGTM!