title: How to pass a count of observations to the facet label?
body: <p>I would like to add a count of observations in each facet to the "title" of each facet. For instance, I have this:</p>
  
  <pre><code>library(tidyverse)    
  
  mtcars %&gt;% 
    ggplot(aes(x = cyl)) + geom_bar()+
    facet_wrap(~carb)
  </code></pre>
  
  <p>and I would like to add the frequencies from the below function to each label</p>
  
  <pre><code>table(mtcars$carb)
   1  2  3  4  6  8 
   7 10  3 10  1  1 
  </code></pre>
  
  <p>Thus the label for 1st row 1st column should be <code>1; n=7</code> the 1st row 2nd column <code>2; n=10</code> etc...</p>