implement DatasetDict.shuffle

[ArneBinder]

TODO:

• add test(s)

[codecov]

Codecov Report

Attention: Patch coverage is 20.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 91.79%. Comparing base (e1db8f3) to head (ba1168d).

Files with missing lines	Patch %	Lines
src/pie_datasets/core/dataset_dict.py	20.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #154      +/-   ##
==========================================
- Coverage   92.19%   91.79%   -0.41%     
==========================================
  Files          10       10              
  Lines         897      902       +5     
==========================================
+ Hits          827      828       +1     
- Misses         70       74       +4     

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