title: R ggplot2 not display unicode font from dataframe correctly
body: <p>Please help check this issue and recommend any library to make it work. I have used showtext library but not help.</p>
  <p><a href="https://i.stack.imgur.com/19Avo.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/19Avo.png" alt="enter image description here" /></a></p>
  <p><a href="https://i.stack.imgur.com/iIfDM.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/iIfDM.png" alt="enter image description here" /></a></p>
  <h2>Sample Data &amp; Code</h2>
  <pre><code>category_name     total_readers
  មនោសញ្ចេតនា​            267867
  ស្នេហា                 239880
  ព្រឺព្រួច                 222031
  អាថ៌កំបាំង               127858
  គុននិយម               101888
  
  df %&gt;% 
    ggplot(aes(area = total_readers, fill = category_name, label = category_name)) +
    geom_treemap() + theme(legend.position = &quot;bottom&quot;, ) +
    geom_treemap_text(fontface = &quot;italic&quot;, colour = &quot;white&quot;, place = &quot;centre&quot;, grow = FALSE)
  </code></pre>