Add unit test snippet

[gengjiawen]

Test every component looks have a lot in common, can we make this a snippet ?

import Vue from 'vue'
import HelloWorld from '@/components/HelloWorld'

describe('HelloWorld.vue', () => {
  it('should render correct contents', () => {
    const Constructor = Vue.extend(HelloWorld)
    const vm = new Constructor().$mount()
    expect(vm.$el.querySelector('.hello h1').textContent)
      .to.equal('Welcome to Your Vue.js App')
  })
})

[sdras]

This is a fantastic idea. I'll definitely include it. I'll also accept a PR, if anyone is interested. Thanks!

[sdras]

Added in! You may have to restart VS Code to get it. I put in some tab markers for the component, etc, let me know if everything works ok.

Thanks!