title: Add line break after caption title in R Markdown
body: <p>I am wanting to change the styling of captions in the R Markdown output, and have two requests:</p>
  
  <ol>
  <li>How do you make the caption label bold?</li>
  <li>How can you add a linebreak after the caption label? For example, I want to enter a line between "Table 1" and the caption.</li>
  </ol>
  
  <p>Here is an example:</p>
  
  <pre><code>caption &lt;- 
    " April is the cruellest month, breeding
      Lilacs out of the dead land, mixing
      Memory and desire, stirring
      Dull roots with spring rain.
      Winter kept us warm, covering
      Earth in forgetful snow, feeding
      A little life with dried tubers.
      Summer surprised us, coming over the Starnbergersee
      With a shower of rain; we stopped in the colonnade,
      And went on in sunlight, into the Hofgarten,
      And drank coffee, and talked for an hour.
      Bin gar keine Russin, stamm’ aus Litauen, echt deutsch.
      And when we were children, staying at the arch-duke’s,
      My cousin’s, he took me out on a sled,
      And I was frightened. He said, Marie,
      Marie, hold on tight. And down we went.
      In the mountains, there you feel free.
      I read, much of the night, and go south in the winter."
  
  kable(mtcars, format = 'latex', caption = caption)
  </code></pre>