[FEATURE] Rug Implementation

[rsh52]

Feature Request Description

"Rugs" can be a great way to view density along the axes of a graph. This may be non-standard for swimmer plots, but thinking in terms of high-density adverse event periods, it could be useful to have an x-axis "rug" that helps show concentration of specific event types. Here's an example from the ggdensity README:

Checklist

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