Add SM_kWkZ_UFO package to MadGraph Models.

This package allows modified Higgs couplings to W and Z bosons in the kappa framework. It will be used by the VBF VH(bb) analysis. Author: Yongcheng Wu, ycwu0830@gmail.com Paper: https://arxiv.org/abs/2006.09374 Received via private communication with the author. I will encourage him to post it publicly.