Add heading id links

js/heading-links.js

@@ -0,0 +1,12 @@
+(function() {
+  var els = document.querySelectorAll('.post-content [id]');
+  var headings = Array.prototype.slice.call(els);
+
+  headings.forEach(function(head) {
+    var link = document.createElement('a');
+    link.className = 'heading-link';
+    link.href = '#' + head.id;
+
+    head.appendChild(link);
+  });
+}());