add extra_js block in base template

Former-commit-id: 7c46cbb220129665b137278ee1e385a22540d4b2

ippisite/ippidb/templates/base.html

@@ -19,7 +19,7 @@
         <script src="/static/chartjs/Chart.bundle.js"></script>
 
         <script src="/static/js/ippidb.js" type="text/javascript"></script>
-
+        {% block extra_js %}{% endblock %}
 
         <script type="text/javascript">
             var modifyUrl = function(paramName, paramValue){