website: Link from Configuration index to Resource page

Since the index page is long, by the time the reader reaches the end of
it the relevant portion if the navigation is unlikely to be visible. To
compensate for this, we'll link to the first sub-section and thus give
the user an opportunity to notice the navigation structure for the rest
of the pages.

website/docs/configuration/index.html.md

@@ -131,3 +131,4 @@ resource "aws_subnet" "az" {
 
 For more information on the configuration elements shown here, use the
 site navigation to explore the Terraform language documentation sub-sections.
+To start, see [_Resource Configuration_](./resources.html).