We need to introduce a wrapper for a `<router-view>` component of the vue-router. [It has been changed in vue-router 4](https://router.vuejs.org/guide/migration/#router-view-keep-alive-and-transition) to support `<keep-alive>` only as a child component. The new wrapper should support both vue-router 3 and 4 and support `<keep-alive>`.