Need theme setting for right/top ticks

So you can do (e.g.)

```
ggplot(mpg, aes(displ, hwy)) +
  geom_point() +
  geom_hline(yintercept = 235 / l_breaks, colour = "pink") +
  scale_y_continuous(
    "mpg",
    sec.axis = sec_axis(~ 235 / ., name = "l / 100 km", breaks = l_breaks)
  ) +
  theme(
    axis.text.y.right = element_text(colour = "pink"), 
    axis.ticks.y.right = element_line(colour = "pink")
  )
```