Add Submit link

People can submit their sites to the Showcase via a Pull Request.

Author: csswizardry

demo/index.html

@@ -39,6 +39,7 @@
     h1, h2,
     p,
     pre,
+    ul,
     .c-snippet,
     .c-video > video,
     .c-video >img {
@@ -535,6 +536,8 @@ <h2 id=showcase>Showcase</h2>
     })();
   </script>
 
+  <p><small><a href=https://github.com/csswizardry/Obs.js/fork>Submit your site.</a></small></p>
+