Add blockers_visible to features list when it's enabled

lib/pleroma/web/mastodon_api/views/instance_view.ex

@@ -65,6 +65,9 @@ def features do
       "shareable_emoji_packs",
       "multifetch",
       "pleroma:api/v1/notifications:include_types_filter",
+      if Config.get([:activitypub, :blockers_visible]) do
+        "blockers_visible"
+      end,
       if Config.get([:media_proxy, :enabled]) do
         "media_proxy"
       end,