### What problem does this feature solve? 嵌套路由的情况下,我想要动态获取菜单,这些每个菜单对应一个vue文件,我想把他们作为子路由添加到一个已存在的路由下面. ### What does the proposed API look like? addRoutes(route,parent) <!-- generated by vue-issues. DO NOT REMOVE -->