Improve add-on products

src/pretix/static/pretixpresale/scss/_cart.scss

@@ -58,6 +58,11 @@
     &.has-downloads .product {
         width: percentage((5 / $grid-columns));
     }
+    .addon-signifier {
+        display: inline-block;
+        padding-left: 10px;
+        font-weight: bold;
+    }
 }
 
 @media(max-width: $screen-sm-max) {
@@ -75,4 +80,4 @@
             clear: both;
         }
     }
-}
+}