update to newer node version

azure-pipelines.yml

@@ -1,12 +1,12 @@
 # Builds and publishes the Monaco Editor website
 
 pool:
-  vmImage: 'Ubuntu-16.04'
+  vmImage: 'ubuntu-latest'
 
 steps:
 - task: NodeTool@0
   inputs:
-    versionSpec: '8.x'
+    versionSpec: '12.x'
   displayName: 'Install Node.js'
 
 - script: |
@@ -18,4 +18,4 @@ steps:
     ./build/publish-website.sh
   env:
     GITHUB_TOKEN: $(GITHUB_TOKEN)
-  displayName: 'Publish website'
+  displayName: 'Publish website'