added community mailing list link

index.html

@@ -98,5 +98,17 @@ <h2>Express & Exchange</h2>
 <section class="call-to-action text-white text-center">
   <div class="overlay"></div>
   <div class="container">
+    <div class="row">
+      <div class="col-xl-9 mx-auto">
+        <h2 class="mb-4">Subscribe to Community Emails</h2>
+      </div>
+      <div class="col-md-10 col-lg-8 col-xl-7 mx-auto">
+        <a href="mailto:community+subscribe@cyberdomainontology.org">
+          <button type="submit" class="btn btn-block btn-lg btn-primary">
+            Subscribe to Community Emails
+          </button>
+        </a>
+      </div>
+    </div>
   </div>
 </section>