Add mastodon link

New social network!

_data/navigation.yml

@@ -130,7 +130,8 @@ social_links:
     href: https://gitlab.gnome.org/GNOME/gtk/
   - icon: fab fa-discourse
     href: https://discourse.gnome.org/c/platform/core/
-
+  - icon: fab fa-mastodon
+    href: https://floss.social/@GTK
 
 # read out the CONTRIBUTING.md to know how to add documentation pages to the website
 

_includes/footer.html

@@ -50,7 +50,7 @@ to make changes related to the content, edit the `_data/navigation.yml`
         <ul class="list-unstyled list-inline text-small">
           {% assign social_links = site.data.navigation.social_links %}
           {% for link in social_links %}
-            <li class="list-inline-item"><a href="{{ link.href }}" class="text-muted text-primary"><i class="{{ link.icon }}"></i></a></li>
+            <li class="list-inline-item"><a href="{{ link.href }}" rel="me" class="text-muted text-primary"><i class="{{ link.icon }}"></i></a></li>
           {% endfor %}
         </ul>
       </div>