Add real icon request link

_includes/request.html

 <section class="section request">
   <div class="container request-container">
     <h2 class="request-heading">Don't see the icon you need?</h2>
-    <a class="button button-secondary" href="#">Request an icon</a>
+    <a class="button button-secondary" href="https://github.com/colebemis/feather/issues/new" target="_blank">Request an icon</a>
   </div>
 </section>
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