Insert scheduled downtime infos from cloud calendar

Change-Id: I8e4524126c08c4b89298e29b4c17588ef3997b71
diff --git a/templates/de/about.html.ep b/templates/de/about.html.ep
index 48356ca..8533e35 100644
--- a/templates/de/about.html.ep
+++ b/templates/de/about.html.ep
@@ -16,4 +16,8 @@
     Es können sich jederzeit unangekündigt Dinge ändern und auch ein kompletter Ausfall über längere Zeit lässt sich nicht mit Sicherheit ausschließen.
     Wenn Sie DeReKoVecs längerfristig für eigene Forschungen verwenden wollen, sprechen Sie uns bitte an.
 </p>
+<h3>Geplante Ausfallzeiten</h3>
+<dl id="downtimes">
+    <dt></dt><dd>–</dd>
+</dl>
 </html>
diff --git a/templates/en/about.html.ep b/templates/en/about.html.ep
index fd2fb7e..8492134 100644
--- a/templates/en/about.html.ep
+++ b/templates/en/about.html.ep
@@ -16,4 +16,8 @@
     Things can change unannounced at any time and even a complete breakdown over a longer period of time cannot be excluded with certainty.
     If you would like to use DeReKoVecs for your own research in the longer term, please contact us.
 </p>
+<h3>Scheduled downtimes</h3>
+<dl id="downtimes">
+    <dt></dt><dd>–</dd>
+</dl>
 </html>
diff --git a/templates/index.html.ep b/templates/index.html.ep
index d6c9ff2..4597a19 100644
--- a/templates/index.html.ep
+++ b/templates/index.html.ep
@@ -10,6 +10,14 @@
     <script src = "https://cdn.datatables.net/fixedcolumns/3.2.5/js/dataTables.fixedColumns.min.js"></script>
     <script src = "https://cdn.datatables.net/plug-ins/1.10.18/sorting/scientific.js"></script>
     <script src='https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js?config=TeX-MML-AM_CHTML'></script>
+     <script src="https://cdnjs.cloudflare.com/ajax/libs/ical.js/1.5.0/ical.js"
+      integrity="sha512-UxWd2RMDGpYwYuDeU2Fs+nd51gw4ZLQY0D9wWZ3NuanNSk6QQmWCZ6C+rvI0lJ/b/nZtBQ8RVESA9DN9r65dUg=="
+      crossorigin="anonymous" referrerpolicy="no-referrer"></script>
+    <script
+      src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.4/moment-with-locales.min.js"
+      integrity="sha512-42PE0rd+wZ2hNXftlM78BSehIGzezNeQuzihiBCvUEB3CVxHvsShF86wBWwQORNxNINlBPuq7rG4WWhNiTVHFg=="
+      crossorigin="anonymous" referrerpolicy="no-referrer"></script>
+    <script src="js/calendar-events.js"></script>
     <link rel="stylesheet" href="https://cdn.datatables.net/1.10.18/css/jquery.dataTables.min.css">
     <link rel="stylesheet" href="/derekovecs/css/derekovecs.css">
     <script
@@ -41,6 +49,7 @@
      }
      
      $(document).ready(function() {
+       insertCalendarEvents(document.getElementById('downtimes'), "<%= $downtime_calendar_url %>");
 
        $('#firstable').hide();
        //Set up a callback to hear back when MathJax is done rendering the equations