Fixed setting content of countdown span

Signed-off-by: Jim Martens <github@2martens.de>

_assets/javascripts/main.js

@@ -39,7 +39,7 @@ $(function() {
                         last: " und ",
                         delim: ", "});
     let counterID = countdown(function(timestamp) {
-            countdownSpan.innerText = timestamp.toString();
+            countdownSpan.html(timestamp.toString());
         }, new Date(2019, 5, 26, 18, 0),
         countdown.DAYS |
         countdown.HOURS |