JS: Support @Component classes in Vue

[asgerf]

Adds support for Vue component implemented as a class decorated with @Component

For example

<template>
    <p v-html="dataA"/>
</template>
<script>
  import Vue from 'vue'
  import Component from 'vue-class-component'

  @Component
  export default class MyComponent extends Vue {
    message: string = 'Hello!'

    get dataA() {
      return 42; // flows to 'dataA`
    }
  }
</script>
<style>
</style>

[asgerf]

PR was included in this evaluation

[erik-krogh]

It took a while, but I think I understand it all.
And it all looks good to me.