Use vertical white lines instead of axis lines for cleaner charts

[@hsinchohuang8741]

very clear and straightforward 🎉

[@wolfgangr.9593]

hm, i think it would be nicer to use
theme(
panel.ontop = TRUE,
panel.grid.major.y = element_blank(),
panel.grid.major.x = element_line(color = "white", linewidth = 0.25),
...
)
instead of the whole geom_vline(...).
That way you can control the breaks and labels of the x axis by scale_x_continuous(...)