Update config to enable docfx v3

Author: VSC-Service-Account

.openpublishing.publish.config.json

@@ -5,7 +5,9 @@
       "build_source_folder": ".",
       "build_output_subfolder": ".",
       "locale": "en-us",
-      "xref_query_tags": ["/uwp/api"],
+      "xref_query_tags": [
+        "/uwp/api"
+      ],
       "monikers": [],
       "moniker_ranges": [],
       "open_to_public_contributors": true,
@@ -90,5 +92,8 @@
       "target_framework": "net45",
       "version": "latest"
     }
-  ]
+  ],
+  "docs_build_engine": {
+    "name": "docfx_v3"
+  }
 }