message: docs: update status
diff: ## Status: Beta
  -The current codebase has most of the existing features on Vue Router v3.x and is usable. It supports all the [merged RFCs](https://github.com/vuejs/rfcs/pulls?q=is%3Apr+is%3Amerged+label%3Arouter).
  +- Most RFCs have been merged.
  +- All [merged RFCs](https://github.com/vuejs/rfcs/pulls?q=is%3Apr+is%3Amerged+label%3A3.x+label%3Arouter) have been implemented.
  +- Vue CLI now has experimental support via [vue-cli-plugin-vue-next](https://github.com/vuejs/vue-cli-plugin-vue-next).
  +- Check the [playground](https://github.com/vuejs/vue-router-next/tree/master/playground) or [e2e tests](https://github.com/vuejs/vue-router-next/tree/master/e2e/modal) for a usage example.
  -Since the library is still unstable **and because we want feedback** on bugs and missing features, **it will probably go through a few breaking changes**.
  -
  -Check the [playground](https://github.com/vuejs/vue-router-next/tree/master/playground) or [e2e tests](https://github.com/vuejs/vue-router-next/tree/master/e2e/modal) for a usage example.
  -
  -## Known issues
  +## Know issues
  ### Breaking changes compared to vue-router@3.x
  