Update 3.0.md

added the vendor extension to externalResources

Author: micheldumontier

versions/3.0.md

@@ -206,7 +206,7 @@ Field Name | Type | Description
 ##### smartAPI Fields
 Field Name | Type | Description
 ---|:---:|---
-<a name="oasExternalResources"></a>externalResources | [[External Resource Object](#externalResourceObject)] | A list of external resources pertinent to the API.
+<a name="oasExternalResources"></a>x-externalResources | [[External Resource Object](#externalResourceObject)] | A list of external resources pertinent to the API.
 
 This object can be extended with [Specification Extensions](#specificationExtensions).