[30] Rename basis function function interface to `vander`

[MothNik]

This pull request renames the basis computing functions for the Hermite function and Chebyshev polynomial basis to vander to be more consistent with NumPy that makes the name show that it computes a Vandermonde matrix.

The class interfaces are left untouched.

Prepares #30

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Files	Coverage Δ
src/robust_fourier/__init__.py	100.00% <ø> (ø)
...c/robust_fourier/chebyshev_polynomials/__init__.py	100.00% <100.00%> (ø)
..._fourier/chebyshev_polynomials/_class_interface.py	100.00% <100.00%> (ø)
...t_fourier/chebyshev_polynomials/_func_interface.py	100.00% <100.00%> (ø)
...bust_fourier/chebyshev_polynomials/_numba_funcs.py	100.00% <100.00%> (ø)
...bust_fourier/chebyshev_polynomials/_numpy_funcs.py	100.00% <100.00%> (ø)
src/robust_fourier/hermite_functions/__init__.py	100.00% <ø> (ø)
...bust_fourier/hermite_functions/_class_interface.py	100.00% <100.00%> (ø)
...obust_fourier/hermite_functions/_func_interface.py	100.00% <100.00%> (ø)
...c/robust_fourier/hermite_functions/_numba_funcs.py	100.00% <100.00%> (ø)
... and 1 more