permutation tests

[enryH]

Description

Add a subpackage (as new model) to core.

Tasks Checklist

• The folder names defines the name of the subpackage (module)
• Add the user-facing functions to the __init__.py in the new folder, so that
  they are available when the subpackage is imported.
• Used pydantic since only dictionary outputs in my learning example...
  Create Pandera schema in a file with subpackage name in the src/acore/types folder.
  Optimal is to have only one output schema of results per subpackage or module.
• Add a relatively small and public dataset to the data folder, or reuse an existing one for testing
• Create an api example jupyter notebook in the docs/api_examples folder with that data
• Use jupytext to sync the Jupyter notebook with a Python script
• Update index.rst file in the docs folder with the new example
• Create test script in the /test folder with the name of the subpackage or module
  using pytest or unittests to test your new functionality.