General Issue: Store all vx data creation scripts

[bms63]

Background Information

We are making a lot of dummy vx data. We need to make sure the scripts that create these datasets are centrally located and changes tracked (version control!). Also, if updates are needed then anyone can do it.

Definition of Done

All scripts are stored in inst/create_vx_data folder.

@pharmaverse/admiralvaccines another easy task to take on that will greatly help the whole team!