ci: set up a lint job (#14536)

.vsts/lint.yml

@@ -0,0 +1,17 @@
+# Starter pipeline
+# Start with a minimal pipeline that you can customize to build and deploy your code.
+# Add steps that build, run tests, deploy, and more:
+# https://aka.ms/yaml
+
+pool:
+  vmImage: 'Ubuntu 16.04'
+
+steps:
+- bash: |
+    git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git "${AGENT_BUILDDIRECTORY}/depot_tools"
+    echo "##vso[task.setvariable variable=PATH]$PATH:${AGENT_BUILDDIRECTORY}/depot_tools"
+  name: Setup_depot_tools
+
+- bash: |
+    npm install
+    npm run lint