site/layouts: add new FSC extension

We use a custom style block in the base that defaults to ISEAL, but
gets overridden in the FSC layout. Layout is determined in the term
frontmatter, either "home" or "fsc".

site/layouts/_default/home.html

@@ -147,6 +147,10 @@
           </div>
         </div>
 
+        <h2 id="schema-extensions">Schema Extensions</h2>
+        <ul>
+          <li><a href="{{ .Site.BaseURL }}/fsc">Forest Stewardship Council</a></li>
+        </ul>
         <h2 id="feedback">Feedback</h2>
         <p>If you have questions/comments please contact ____.</p>
       </main>