Create border and title for each column in `facet_wrap`

I want to put black borders with labels and titles around each facet in facet_wrap. Something similar to this:

Sample data:

library(tidyverse)

mtcars %>% 
  mutate(gear = factor(gear, levels = c(4, 3, 5))) %>%
  ggplot(aes(mpg, disp)) + 
  geom_point() + 
  geom_smooth(method = "lm") + 
  facet_wrap(~am + gear)