Add support for polars

[kklein]

Checklist

• Added a CHANGELOG.rst entry

[codecov]

Codecov Report

Attention: Patch coverage is 88.63636% with 5 lines in your changes missing coverage. Please review.

Project coverage is 94.58%. Comparing base (acc246c) to head (37862d7).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
metalearners/_utils.py	82.60%	4 Missing ⚠️
metalearners/data_generation.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #90      +/-   ##
==========================================
- Coverage   94.73%   94.58%   -0.16%     
==========================================
  Files          15       15              
  Lines        1806     1827      +21     
==========================================
+ Hits         1711     1728      +17     
- Misses         95       99       +4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.