Display total hours played on homepage

src/web/tracker/templates/index.html

@@ -5,7 +5,7 @@
 {% block content %}
 <div class="text-slate-300 mx-auto max-w-screen-lg text-center">
 {% if session_count > 0 %}
-You have played a total of {{ session_count }} sessions.
+You have played a total of {{ session_count }} sessions for a total of {{ total_duration }}.
 {% else %}
 Start by clicking the links at the top. To track playtime, you need to have at least 1 owned game.
 {% endif %}