Synthetic alphas and covariance for BAO from GCspectro

Includes measurements of the post-reconstruction BAO alpha parameters and their covariances, following the agreed upon datamodels. redshifts = [1.0, 1.2, 1.4, 1.65] parameters = { 'H0': 67.0, 'Omega_cdm0': 0.27, 'Omega_b0': 0.049, 'Omega_k0': 0.0, 'mnu': 0.0, 'w0': -1.0, 'wa': 0.0, 'ns': 0.96, 'As': 2.1e-9, 'gamma_MG': 0.545,} The measurements assumed fiducial cosmology = true cosmology, so alpha=1 for all values.