[minor] point github logo @ graphql api landing page

it's easy for folks to get lost off the main site, thought it might be helpful to point them at our landing page for graphql in the dev site

Author: brandonblack

site/index.html.js

@@ -543,7 +543,7 @@ public class Character {
               <img src="/img/logos/twitter.png" title="Twitter" className="round" />
             </a>
             {/**/}
-            <a href="https://github.com/" target="_blank">
+            <a href="https://developer.github.com/early-access/graphql" target="_blank">
               <img src="/img/logos/github.png" title="GitHub" className="round" />
             </a>
             {/** /}