Enable dependabot for Azure Repos

.azuredevops/dependabot.yml

@@ -0,0 +1,9 @@
+# Please see the documentation for all configuration options:
+# https://eng.ms/docs/products/dependabot/configuration/version_updates
+
+version: 2
+updates:
+- package-ecosystem: nuget
+  directory: /
+  schedule:
+    interval: monthly