HepMC3 event record library: ViewerExample -> include Relation

HepMC3 event record library

### ViewerExample → include Relation

File in examplesViewerExample | Includes file in include
--- | ---
src / HepMC3ViewerFrame.cc | HepMC3 / GenEvent.h
src / HepMC3ViewerFrame.cc | HepMC3 / GenParticle.h
src / HepMC3ViewerFrame.cc | HepMC3 / GenVertex.h
src / HepMC3ViewerFrame.cc | HepMC3 / ReaderFactory.h
include / HepMC3ViewerFrame.h | HepMC3 / GenEvent.h
include / HepMC3ViewerFrame.h | HepMC3 / Reader.h