Move about link to config

_config.yml

@@ -5,6 +5,7 @@ baseurl: ""
 url: "http://yourdomain.com"
 twitter_username: FreifunkHH
 github_username:  freifunkhamburg/start-ffhh
+about_page:       https://hamburg.freifunk.net/
 
 # Build settings
 markdown: kramdown

_includes/header.html

@@ -5,7 +5,7 @@
     <a class="site-title" href="{{ site.baseurl }}/">{{ site.title }}</a>
 
     <nav class="site-nav">
-        <a class="page-link" href="https://hamburg.freifunk.net/">About</a>
+        <a class="page-link" href="{{ site.about_page }}">About</a>
     </nav>
 
   </div>