Add EEPs link

Author: hiroyuki-sato

docs/index.html

@@ -22,6 +22,9 @@ <h2>Development Guides</h2>
   <ul>
     <li><a href="https://docs.google.com/document/d/1oKpvgstKlgmgUUja8hYqTqWxtwsgIbONoUaEj8lO0FE/edit">Embulk Input Plugin Development Guide</a></li>
   </ul>
+  <ul>
+    <li><a href="https://github.com/embulk/embulk/blob/master/docs/eeps/eep-0000.md">EEPs(Embulk Enhancement Proposals)</a></li>
+  </ul>
 </section>
 
 <section id="libraries">