Use more epidemiological themed examples in demo vignette

[Bisaloo]

The demo vignette includes examples for each category of plot we expect but these examples are taken straight from ggplot2 docs.

This works for the short term but in the medium term, it would probably make more sense to add epi specific examples, with datasets from, e.g., the outbreaks package.

[pratikunterwegs]

Happy to add plots under 'line' and 'bar/column' taken from {finalsize}, {cfr}, and {epidemics} - are you happy to have these added as dependencies under Suggests?

I'm also happy to add:

• choropleth maps for Covid if you are happy to accept {covidregionaldata} as a dependency, or point me to another data source?
• network diagrams if I could be pointed to an appropriate dataset, e.g. of contact tracing data.

[Bisaloo]

Since this package is likely to be pulled by every other Epiverse-TRACE package (as Suggests but still), let's keep it extra lightweight and limit ourselves to a single data package, with minimal code to produce simple plots, if possible.

If not, it's probably best to stick with generic, non-epi specific examples for now, since they already serve their purpose well. This issue is more of a "nice to have" rather than an urgent need.

I was already thinking to remove the extra packages in Suggests (ggraph, tidygraph, sf & maps) and include the demo in a separate pkgdown-only article for these plots to.

[pratikunterwegs]

That's fair - {cfr} could fit the bill as it includes Covid incidence data, and the estimates are suitable for line and column plots. Uncertainty could be used to show geom_ribbon()/geom_area(). Onset to death distributions can be shown for distributions. I don't have good options for densities or heatmaps. Also happy to add plots from another package, e.g. {incidence2}.

It would be easy to write a small SIR model inline, to show modelling output if that's useful. A specific subset of this is model outputs with stochastic or parameter uncertainty, which could be shown with transparent lines - a somewhat more complex model would be necessary there.

There would also need to be a section for rectangle plots, as this is one way we currently display interventions (using geom_rect(), not geom_area()).

[pratikunterwegs]

A separate epi plot gallery repo is also a good idea - I don't have strong preferences, but agree that ideally this package would have very very few dependencies.

[rozeggo]

I do think we should keep this as minimal as possible, given that there are a lot of resources out there showing the best ways to plot/display data - we dont need to provide a kind of pseudo-training demo on the best ways to visualise. I think we want to focus on showcasing the theme.