Track dates of English school holidays

Fixes #168

templates/trip_page.html

@@ -399,6 +399,23 @@
     {% endif %}
     </div>
 
+    <div class="mt-3">
+    <h4>UK school holidays (Bristol)</h4>
+    {% if school_holidays %}
+      <table class="table table-hover w-auto">
+      {% for item in school_holidays %}
+        <tr>
+          <td class="text-end">{{ display_date(item.as_date) }}</td>
+          <td>to {{ display_date(item.end_as_date) }}</td>
+          <td>{{ item.title }}</td>
+        </tr>
+      {% endfor %}
+      </table>
+    {% else %}
+      <p>No UK school holidays during trip.</p>
+    {% endif %}
+    </div>
+
     {{ next_and_previous() }}
 
     </div>