Add examples of validators to documentation (#1702)

* Add examples of validators to documentation

* Update to move examples under guides section

* Update based on PR comments

* Update order of guides to place validation examples under linters

* Touch up based on PR comments

Author: hpmellema

docs/source-2.0/guides/index.rst

@@ -8,6 +8,7 @@ Guides
     building-models/index
     using-code-generation/index
     model-linters
+    model-validation-examples
     evolving-models
     style-guide
     converting-to-openapi