Update azure-pipelines.yml for Azure Pipelines (#419)

* Update azure-pipelines.yml for Azure Pipelines

* add bump to 6.11.1

azure-pipelines.yml

@@ -54,6 +54,9 @@ jobs:
           versionSpec: "8.x"
         displayName: "Install Node.js"
 
+      - script: npm install -g npm@6.11.1
+        displayName: (fix)bump to npm@6.11.1
+
       - script: npm install
         displayName: "npm install"