ggplot gallery: lollipop edits

[OskaratOmni]

Reviewer comments:

Add a title

Make the dot large enough that the number can fit inside it

Can we add an option to change certain bar colors or add a vertical line for a benchmark if needed?

[dgkeyes]

I've done all of this. See https://stupendous-biscuit-9f1c75.netlify.app/ggplot/graph_lollipop.html

The only thing I haven't changed is adding instructions to change certain bar colors. This is a general thing that is covered on the guidelines page. While we could show it for each bar chart type, it becomes quite duplicative.