Updated technique for the simulation of dark bremmstrahlung in GEANT4

The G4DarkBreM software package simulates dark bremmstrahlung of electrons and muons off target nuclei by embedding a library of interaction vertices generated by MadGraph/MadEvent within the GEANT4 detector simulation framework. A recent update to the package enables scaling of the outgoing dark photon momentum, whereas previously only the outgoing lepton momentum was scaled. Scaling of dark photon kinematics achieves precision typically better than 10% compared with dedicated samples, commensurate with previous results. This extension improves the package's utility for simulating signal processes in a class of dark matter searches in which dark photons decay visibly within the detector.