Use https links in the footer.

Author: sjrd

_includes/footer.html

@@ -13,10 +13,10 @@ <h4>COMMUNITY</h4>
 
                 <div class="hline-w"></div>
                 <a class="grey-text text-lighten-3" href="https://discord.com/invite/scala">#scala-js on Discord</a><br/>
-                <a class="grey-text text-lighten-3" href="http://stackoverflow.com/questions/tagged/scala.js">Stackoverflow</a><br/>
+                <a class="grey-text text-lighten-3" href="https://stackoverflow.com/questions/tagged/scala.js">Stackoverflow</a><br/>
                 <a class="grey-text text-lighten-3" href="https://groups.google.com/forum/?fromgroups#!forum/scala-js">Mailing list</a><br/>
-                <a class="grey-text text-lighten-3" href="http://twitter.com/scala_js">Twitter <i aria-hidden="true" class="fa fa-twitter"></i></a><br/>
-                <a href="http://github.com/scala-js/scala-js">GitHub <i aria-hidden="true" class="fa fa-github"></i></a>
+                <a class="grey-text text-lighten-3" href="https://twitter.com/scala_js">Twitter <i aria-hidden="true" class="fa fa-twitter"></i></a><br/>
+                <a href="https://github.com/scala-js/scala-js">GitHub <i aria-hidden="true" class="fa fa-github"></i></a>
             </div>
             <div class="col-md-4">
             </div>