Merge branch 'develop' into 'main'

include/tadah/models/cutoffs.h

include/tadah/models/descriptors/d_basis_functions.h

include/tadah/models/linear_regressor.h

include/tadah/models/m_krr_train.h

include/tadah/models/ols.h

include/tadah/models/ridge_regression.h

src/cutoffs.cpp

src/d3_base.cpp

src/kern_base.cpp

tests/test_cutoffs.cpp

tests/test_d2.cpp

tests/test_dm.cpp

tests/test_factory_cutoffs.cpp

tests/test_ols.cpp