Add itemcount (Items, excluding AddOns) to fragment_cart (#1514)

* Add itemcount (Items, excluding AddOns) to fragment_cart

* Simplify itemcount

src/pretix/presale/views/__init__.py

@@ -173,6 +173,7 @@ class CartMixin:
             'minutes_left': minutes_left,
             'seconds_left': seconds_left,
             'first_expiry': first_expiry,
+            'itemcount': sum(c.count for c in positions if not c.addon_to)
         }