vue嵌套路由（父子路由）

配置父子路由关系，A.vue和B.vue是Main.vue的子组件:

{
      path: '/main/',
      name: 'main',
      component: () => import('components/Main.vue'),
      children: [
        {
          path: 'a',
          name: 'a',
          component: () => import('components/A.vue')
        },
        {
          path: 'b',
          name: 'b',
          component: () => import('components/B.vue')
        }
      ]
    }
{
      pat