title: How to set padding in header cells of htmlTable package?
body: <p>I am using htmlTable package in my rmarkdown files. For setting cell padding I use this piece of code: </p>
  
  <pre><code>htmlTable(..., css.cell = "padding-left: .5em; padding-right: .2em;")
  </code></pre>
  
  <p>How can I do something similar on the header cells? </p>