make_labs.RdInternal, called by `plot_timeline`.
make_labs(description, description_width, ref_number)The text for the items to be shown beneath the images. Should be a character vector of the same length as `image_path`.
Width of the description text in characters to wrap the text in the labels.
A string of the number for reference. If NA, then the reference will not be included in the plot.
A character vector of plotmath, to enable superscripts, italics, and text wrapping.