no-dupe-keys rule doesn't work for vue templates

[MarvinXu]

Tell us about your environment

• ESLint version: 5.9.0
• eslint-plugin-vue version: 5.0.0
• Node version: 10.12.0

What did you do?

I used latest vue-cli to create a demo. https://github.com/MarvinXu/standard-fix/blob/master/src/App.vue#L7

What did you expect to happen? eslint report an error for duplicate key 'test'

What actually happened?

no eslint errors