Gridkit

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Features
- add numpy_id_to_grid_id() to BoundedHexGrid
- add grid_id_to_numpy_id() to BoundedHexGrid

Fixes
- resolve shift in data when using comparisson and mathematical operators on BoudedHexGrid

Documentation
- Add examle on coordinate transformations

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Features
- Resample method for BoundedHexGrid
- Bilinear interpolation method for BoundedHexGrid
- Split ``Interpolate`` method from ``resample`` method
- Codecov integration

CICD
- black and isort checks in test pipeline

Documentation
- Add missing docstrings to resample method

Misc
- reformat python files using black and isort
- move ``Resample`` method one step up in the inheritance hierarchy, to BoundedGrid

Added the basics of Hexagon grids