README has links to non-force-directed beeswarms

[jtrim-ons]

The README has two links to a beeswarm plot on Observable: one in the text and one an image. The current version of the plot on Observable is not force directed, so perhaps it might be confusing for people who want to learn how to create a force-directed beeswarm?

I love the d3-force library but I have mixed feelings about using it for beeswarm plots because the points can be moved slightly away from their correct positions. So I'm not sure about the best way to update the README (or perhaps it's fine the way it is!)