Add custom-fields support for feed items

This just enables the custom fields UI in the feed item edit page.

Author: mecha

src/Modules/FeedItemsModule.php

@@ -199,7 +199,7 @@ public function getFactories()
                     'capability_type' => $c->get('wpra/feeds/items/cpt/capability'),
                     'map_meta_cap' => true,
                     'labels' => $c->get('wpra/feeds/items/cpt/labels'),
-                    'supports' => ['title', 'editor', 'excerpt'],
+                    'supports' => ['title', 'editor', 'excerpt', 'custom-fields'],
                 ];
             },
             /*