Add h2 ids in tutorial list

web/templates/tutorials.html

@@ -1,5 +1,5 @@
 <h1>Tutorials about Hakyll</h1>
-<h2>Tutorial series</h2>
+<h2 id="series">Tutorial series</h2>
 <ul>
     $for(tutorials)$
         $if(isSeries)$
@@ -9,7 +9,7 @@
         $endif$
     $endfor$
 </ul>
-<h2>Other articles</h2>
+<h2 id="articles">Other articles</h2>
 <p>In no particular order:</p>
 <ul>
     $for(tutorials)$
@@ -20,7 +20,7 @@
         $endif$
     $endfor$
 </ul>
-<h2>External articles</h2>
+<h2 id="external-articles">External articles</h2>
 <p>
     These are articles on external blogs. If you wrote a similar article, feel
     free to <a href="http://jaspervdj.be/contact.html">shoot me an email</a> so