gaia-dpci/GaiaXPy: GaiaXPy 2.0.1

Fixed issue in function for computing the inverse of the covariance matrix (get_inverse_covariance_matrix). Fixed issue in function to get chi-squared from an input inverse square root of covariance matrix (get_chi2). Added function to compute the inverse square root of the covariance matrix (get_inverse_square_root_covariance_matrix).