pre and post HTML templates for all txt2tags conversions

Remaining: cleaning of t2t files (remove unnecessary options)

index.html

@@ -30,7 +30,7 @@
       <li><a href="http://cloud.grammaticalframework.org/">GF Cloud</a>
       <li><a href="demos/index.html">Other Demos</a>
     </ul>
-    <a href="http://www.grammaticalframework.org/download/index.html" class="btn btn-primary mb-3 ">
+    <a href="download/index.html" class="btn btn-primary mb-3 ">
       <i class="fas fa-download mr-1"></i>
       Download GF
     </a>
@@ -68,7 +68,10 @@
     <h4>GF</h4>
     <ul>
       <li><a href="doc/gf-developers.html">GF Developers Guide</a>
-      <li><a href="https://github.com/GrammaticalFramework/">GF on GitHub</a>
+      <li><a href="https://github.com/GrammaticalFramework/">
+        GF on GitHub
+        <i class="fab fa-github"></i>
+      </a>
       <li><a href="/~hallgren/gf-experiment/browse/">Browse Source Code</a>
       <li><a href="doc/gf-people.html">Authors</a>
     </ul>
@@ -141,6 +144,8 @@ Don't worry if you don't know most of the references above - but if you do know
 least one, it may help you to get a first idea of what GF is.
 </p>
 
+<hr>
+
 <div class="row">
 
   <div class="col-sm-6">
@@ -345,6 +350,22 @@ least one, it may help you to get a first idea of what GF is.
 
 </div><!-- .container -->
 
+<footer class="bg-light mt-5 py-5">
+  <div class="container mb-5">
+    <div class="row">
+      <div class="col-md-4">
+
+      </div>
+      <div class="col-md-4">
+
+      </div>
+      <div class="col-md-4">
+
+      </div>
+    <div>
+  <div>
+</footer>
+
 <script type="text/javascript">
 var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www.");
 document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E"));