Illustrative demo data

[adamkucharski]

This may already be planned, but would be nice to include some demo data so people can explore functionality without loading their own data. E.g. SORMAS do this quite nicely.

For simplicity, could take a subset from the repo accompanying the now published Legacy study – tagging @thimotei who might be able to suggest a good option.

[hillalex]

Yep, epikinetics package has some data installed with it that would be a good candidate: https://github.com/seroanalytics/epikinetics/tree/main/inst