First draft of elm frontend

This will probably be scrapped or rewritten

jon/templates/entry/index.html

@@ -1,5 +1,16 @@
 {% extends "base.html" %}
 
 {% block content %}
-<a href="/entry/edit-item-data">Neuer Eintrag</a>
+<div class="entry-app"></div>
+<script src="{{ url_for('static', filename='entry.js') }}"></script>
+<script>
+Elm.Entry.init({
+  node: document.querySelector('.entry-app'),
+  flags: {
+    locations: {{ to_json(locations) | safe }},
+    groups: {{ to_json(groups) | safe }},
+    taxGroups: {{ to_json(tax_groups) | safe }}
+  }
+});
+</script>
 {% endblock %}