title: keyboard navigation with arrow keys (next and back) for changing filenames
body: <p>I have a bunch of html files with different file-names, that I need to add an option to use keyboard arrow keys to navigate (previous and next file).</p>
  
  <p>The file-names are not dynamic..  for example: filename.html, anotherfile.html, thirdone.html
  etc.</p>
  
  <p>So I need what's in the .js file for the navigation, and what I should link the previous, next buttons on the html file?</p>