title: kableExtra: Specify the look of selected rows programatically
body: <p>Currently <code>kableExtra</code> 0.5.1 only supports <em>Specify the look of the selected row</em>. I wonder if there is any tweak to specify the look of selected rows programatically like <code>row_spec(x, c(1, 3, 4), bold = TRUE, italic = TRUE)</code>. Thanks</p>
  
  <pre><code>library(knitr)
  library(kableExtra)
  
  x &lt;- knitr::kable(head(mtcars), "latex")
  kableExtra::row_spec(x, 1, bold = TRUE, italic = TRUE)
  </code></pre>