add link to custom data upload session API

Author: markwahl-msft

docs/id-governance/custom-data-resource-access-reviews.md

@@ -117,6 +117,7 @@ After copying both the Access review object, and access review instance object,
     > To confirm all CSVs were uploaded successfully, view the [audit logs](entitlement-management-logs-and-reporting.md).
 1. You have **up to two hours** from the time the review enters the *Initializing* state to complete the upload.
 
+You can also upload custom data via Graph, by creating an upload session and then uploading a CSV file. For more information, see [customDataProvidedResourceUploadSession](/graph/api/resources/customdataprovidedresourceuploadsession?view=graph-rest-beta).
 
 ## Active review state