Alter simulation settings and text to highlight problem of censoring

[athowes]

In the current "get started" vignette (note this issue was highlighted in #59), the simulation settings are such that the extent of biased caused by censoring is less than the extent of biased caused by right truncation. See Figure 2.1:

This is mentioned in the caption of the figure. It could be beneficial to

1. Change the simulation settings to make censoring more of an issue,
2. Extend this figure / section to split out the impact of right truncation and censoring. This may involve plotting more "types" of data, including the continuous data (see e.g. Is there an issue with using a histogram to plot continuous data? #67).

The point is that we don't want readers to go away with the impression that they don't need to adjust for censoring.

[athowes]

Adam to look at Figure 9 in Park et al. SI to decide whether or not to include similar figure in vignette (could be with the changed simulation settings, or without):