2-byte characters are garbled in the plot

[tasasaki-github]

Executing the following code will garble 2-byte characters in the plot:

ggplot(
  data = penguins,
  mapping = aes(x = bill_length_mm, y = body_mass_g)
  ) +
  geom_point(na.rm = TRUE) + 
  labs(caption = "デ ー タ はpalmerpenguinsパッケージより。")

I think drawing with AGG (ragg) will solve the garbled characters, so I would like to see a change so that ragg can be used in positron.

[juliasilge]

We also would like to use ragg for plot rendering and think that would be the best option in the long term. I added your request to #2919. Thanks!