feat: dub refer embed (#20258)

* feat: dub refer embed

* review fix

* review fix

* @dub/embed-core seems not needed

* @dub/embed-core can stay in web

* move refer page out of main-nav

* update yarn lock

* use loading.tsx

---------

Co-authored-by: Peer Richelsen <peeroke@gmail.com>
Co-authored-by: hbjORbj <sldisek783@gmail.com>

.env.example

@@ -117,6 +117,11 @@ NEXT_PUBLIC_PLAIN_CHAT_ID=
 PLAIN_CHAT_HMAC_SECRET_KEY=
 NEXT_PUBLIC_PLAIN_CHAT_EXCLUDED_PATHS=
 
+
+# Dub Config
+DUB_API_KEY=
+NEXT_PUBLIC_DUB_PROGRAM_ID=
+
 # Zendesk Config
 NEXT_PUBLIC_ZENDESK_KEY=
 
@@ -429,6 +434,4 @@ NEXT_PUBLIC_QUERY_AVAILABLE_SLOTS_INTERVAL_SECONDS=
 # Used to invalidate available slots when navigating to booking form
 NEXT_PUBLIC_INVALIDATE_AVAILABLE_SLOTS_ON_BOOKING_FORM=0
 # Used to enable quick availability checks for x% of all visitors
-NEXT_PUBLIC_QUICK_AVAILABILITY_ROLLOUT=10
-
-
+NEXT_PUBLIC_QUICK_AVAILABILITY_ROLLOUT=10