New files
templates/app/base.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Djangocourse</title>
</head>
<body>
<nav>Common navigation bar for all templates</nav>
{% block content %}
{% endblock content %}
<footer>Common footer for all templates</footer>
</body>
</html>