Port Improve Digital: Add iframe user sync (prebid#3913)

Author: AntoxaAntoxic

src/main/resources/bidder-config/improvedigital.yaml

@@ -22,3 +22,7 @@ adapters:
         url: https://ad.360yield.com/server_match?gdpr={{gdpr}}&gdpr_consent={{gdpr_consent}}&us_privacy={{us_privacy}}&gpp={{gpp}}&gpp_sid={{gpp_sid}}&r={{redirect_url}}
         support-cors: false
         uid-macro: '{PUB_USER_ID}'
+      iframe:
+        url: https://ad.360yield.com/user_sync?rt=html&gdpr={{gdpr}}&gdpr_consent={{gdpr_consent}}&us_privacy={{us_privacy}}&gpp={{gpp}}&gpp_sid={{gpp_sid}}&r={{redirect_url}}
+        support-cors: false
+        uid-macro: '{PUB_USER_ID}'