[A11y] improve cart renew confirmation (#5206)

* [A11y] improve cart renew confirmation

* revert time

* add inline-dialog to cart-renewal-button so confirm-button has interactive meaning

src/pretix/presale/templates/pretixpresale/event/fragment_cart.html

@@ -1,4 +1,5 @@
 {% load i18n %}
+{% load icon %}
 {% load eventurl %}
 {% load daterange %}
 {% load safelink %}
@@ -506,10 +507,23 @@
             </p>
             <p>
                 <button class="btn btn-default" type="submit" id="cart-extend-button" aria-describedby="cart-deadline">
-                    <i class="fa fa-refresh" aria-hidden="true"></i> {% trans "Renew reservation" %}
+                    {% icon "refresh" %} {% trans "Renew reservation" %}
                 </button>
             </p>
         </form>
+
+        <dialog role="alertdialog" id="cart-extend-confirmation-dialog" class="inline-dialog" aria-labelledby="cart-deadline">
+            <form method="dialog">
+                <p>
+                    <button class="btn btn-success" autofocus value="OK">
+                        <span role="img" aria-label="{% trans "OK" %}.">
+                            {% icon "check" %}
+                        </span>
+                        {% trans "Reservation renewed" %}
+                    </button>
+                </p>
+            </form>
+        </dialog>
     {% else %}
         <p class="sr-only" id="cart-description">{% trans "Overview of your ordered products." %}</p>
     {% endif %}