[Improvement] Reorganize document (#1066)

docs/markdown/quickstart.en-US.md

@@ -0,0 +1,76 @@
+## Quickstart
+
+### Install
+
+```shell
+npm i vant -S
+```
+
+### Usage
+
+#### 1. Use [babel-plugin-import](https://github.com/ant-design/babel-plugin-import) (Recommended)
+```bash
+# Install babel-plugin-import
+npm i babel-plugin-import -D
+```
+
+```js
+// set babel config in .babelrc or babel-loader
+// Note: Don't set libraryDirectory if you are using webpack 1.
+{
+  "plugins": [
+    ["import", {
+      "libraryName": "vant",
+      "libraryDirectory": "es",
+      "style": true
+    }]
+  ]
+}
+```
+
+Then you can import components from vant, equivalent to import manually below.
+
+```js
+import { Button } from 'vant';
+```
+
+#### 2. Manually import
+
+```js
+import Button from 'vant/lib/button';
+import 'vant/lib/vant-css/base.css';
+import 'vant/lib/vant-css/button.css';
+```
+ 
+#### 3. Import all components
+If you configured babel-plugin-import, you won't be allowed to import all components.
+
+```js
+import Vue from 'vue';
+import Vant from 'vant';
+import 'vant/lib/vant-css/index.css';
+
+Vue.use(Vant);
+```
+
+### CDN
+
+```html
+<!-- import style -->
+<link rel="stylesheet" href="https://unpkg.com/vant/lib/vant-css/index.css" />
+
+<!-- import script -->
+<script src="https://unpkg.com/vant/lib/vant.min.js"></script>
+```
+
+### vue-cli template
+
+```shell
+vue init youzan/vue-cli-template-vant projectName
+```
+
+### rem units
+Vant use `px` as size units by default，you can use tools such as `postcss-pxtorem` to transform units to `rem`.
+
+- [postcss-pxtorem](https://github.com/cuth/postcss-pxtorem)
+- [lib-flexible](https://github.com/amfe/lib-flexible)