Add order_confirmation template

uncloud_v3/app/templates/app/order_confirmation.html

@@ -0,0 +1,13 @@
+<h2>Order Confirmation</h2>
+
+<p>
+Thank you for the order. The details are below:
+</p>
+<div class="order-details">
+    Order ID: {{ product_order.id }}<br/>
+    Product: {{ product_order.product.name }}
+</div>
+<br/>
+<div>
+    <a href="{% url 'index' %}">Go back to the home page</a>
+</div>