feat: add new env variables in env.example file

Author: PaoloRollo

apps/dashboard/.env.example

@@ -108,4 +108,10 @@ STRIPE_SECRET_KEY=""
 
 # required for server wallet management
 NEXT_PUBLIC_THIRDWEB_VAULT_URL=""
-NEXT_PUBLIC_ENGINE_CLOUD_URL=""
+NEXT_PUBLIC_ENGINE_CLOUD_URL=""
+
+# farcaster frame env variables
+NEXT_PUBLIC_APP_URL=
+NEXT_PUBLIC_FARCASTER_HEADER=
+NEXT_PUBLIC_FARCASTER_PAYLOAD=
+NEXT_PUBLIC_FARCASTER_SIGNATURE=