chore(data-format): rnf invoice allow negative line items (#1618)

Author: leoslr

packages/data-format/src/format/rnf_invoice/rnf_invoice-0.0.3.json

@@ -124,7 +124,7 @@
           },
           "unitPrice": {
             "type": "string",
-            "pattern": "^\\d+$"
+            "pattern": "^-?\\d+$"
           },
           "discount": {
             "type": "string",