message: [Doc] update README.md and quickstart
diff: @@ -29,17 +29,6 @@ npm i vant -S
  npm i vant@beta -S
  ```
  -### CDN
  -
  -```html
  -<!-- import style -->
  -<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/vant@beta/lib/index.css" />
  -
  -<!-- import script -->
  -<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.min.js"></script>
  -<script src="https://cdn.jsdelivr.net/npm/vant@beta/lib/vant.min.js"></script>
  -```
  -
  ## Usage
  ### 1. Import on demand
  @@ -102,6 +91,28 @@ Vue.use(Vant);
  > If you configured babel-plugin-import, you won't be allowed to import all components.
  +### 4. CDN
  +
  +```html
  +<!-- import style -->
  +<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/vant@beta/lib/index.css" />
  +
  +<!-- import script -->
  +<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.min.js"></script>
  +<script src="https://cdn.jsdelivr.net/npm/vant@beta/lib/vant.min.js"></script>
  +
  +<script>
  +var Vue = window.Vue;
  +var vant = window.vant;
  +
  +// Register components
  +Vue.use(vant);
  +
  +// Call function components
  +vant.Toast('message');
  +</script>
  +```
  +
  ## Other
  ### Rem units
  