title: Generate table of contents from the yaml header title of a list of R Markdown files
body: <p>Is there a way to generate a list of the yaml header titles from a list of R Markdown files with the means of R? Suppose you have two files</p>
  
  <p>A.Rmd</p>
  
  <pre><code>---
  title: Titel of first file
  ---
  </code></pre>
  
  <p>B.Rmd</p>
  
  <pre><code>---
  title: Titel of second file
  ---
  </code></pre>
  
  <p>Then the list should look like</p>
  
  <pre><code>File |Title
  -----|--------------------
  A.Rmd|Titel of first file
  B.Rmd|Titel of second file
  </code></pre>
  
  <p>Could this list be generated as R Markdown file too - preferable with links to the original files?</p>