Add Gateway Registration section to configuration.md

Added section on Gateway Registration

Author: mkachk

docsource/configuration.md

@@ -5,6 +5,8 @@ This integration allows for the Synchronization, Enrollment, and Revocation of c
 ## Requirements
 
 This integration is tested and confirmed as working for Anygateway REST 24.4 and above. Notice: Keyfactor Anygateway REST 24.4 requires the use of .Net 8.
+## Gateway Registration
+Download the **PCA root certificate** from AWS and have it ready to import into the Gateway **in `.pem` format**.
 
 ## Authentication (Access Key + Secret)