Add customer name mapping info

Added detail around a field we map for Customers which is a nuance in our mapping that a client flagged - it's confusing as we don't map to the company name as a client might expect so I think its worth calling it out.

docs/integrations/accounting/netsuite/oracle-netsuite-integration-reference.md

@@ -125,6 +125,9 @@ When pushing Bill payments to Oracle NetSuite:
 - The supported use cases are paying off a bill with cash and applying a bill credit note to a bill.
 - Applying NetSuite Vendor Prepayments to open bills from vendors is not supported.
 
+## Customers
+When pulling Customers from NetSuite we map CustomerName from CustomerID.
+
 ## Direct costs and direct incomes
 
 :::note Type not supported