Insertion of lenapy Harmo

The lenapy_harmo module provides functionalities for spherical harmonics dataset (clm/slm) and
projections on latitude/longitude grids.

This module includes two classes:

• HarmoSet: Provides methods for handling spherical harmonics decompositions, converting them to grid representations
  and performing operations such as changing reference frames and tide systems.
• HarmoArray: Converts grid representation of a spherical harmonics dataset back to spherical harmonics.

The module is designed to work seamlessly with xarray datasets, enabling efficient manipulation and visualization.