How to position plot.tag and plot.title side-by-side, on the same line

Question

I have created a custom ggplot theme, and would like to position the plot.tag and plot.title next to each other, on the same line. I want to keep the two labels unique from each other as I require different text formats. I also want to keep the tag optional, so if it's not specified in labs(), then the title will be shown by itself in the top-left position.

I've tried: plot.tag.position = 'topleft' but this creates unwanted space to the left of the plot; and plot.tag.position = c(0,1) but this overlaps the tag and title labels (in the code below, I've used this but hacked the title label with spaces).

library(ggplot2)

ggplot(economics, aes(x = date, y = uempmed)) +
  geom_line() +
  labs(title = "                    Median duration of unemployment",
       tag = "Figure 1.0:",
       y = "Weeks") + 
  theme(plot.title.position = 'plot', 
        plot.title = element_text(hjust = 0, vjust = 1, margin = margin(t = 0, r = 0, b = 0, l = 0, unit = 'mm')),
        plot.tag.position = c(0,1), 
        plot.tag = element_text(face = 'bold', hjust = 0, vjust = 1, margin = margin(t = 0, r = 0, b = 0, l = 0, unit = 'mm')))

This is the result that I'm aiming for: