(GH-717) Fix minimum item counts for resources in config doc

This change sets the `minItems` keyword to `0` for the `resources` property
of a configuration document. Prior to this change, the schema specified a
value of `1`, which was inaccurate.

This change fixes #717

Author: michaeltlombardi

schemas/src/config/document.yaml

@@ -321,7 +321,7 @@ properties:
     title:       DSC configuration document resources
     description: Defines a list of DSC resource instances for the configuration to manage.
     type:        array
-    minItems:    1
+    minItems:    0
     items:
       $ref: /<PREFIX>/<VERSION>/config/document.resource.yaml
     # VS Code only