[Doc] add some english documents (#220)

* [bugfix] Checkbox border render error in weixin browser

* [bugfix] TreeSelect dependency path error

* [bugfix] Swipe should clear autoplay timer when destroyed

docs/examples-docs/en-US/card.md

@@ -0,0 +1,75 @@
+<script>
+export default {
+  data() {
+    return {
+      imageURL: '//img.yzcdn.cn/upload_files/2017/07/02/af5b9f44deaeb68000d7e4a711160c53.jpg'
+    }
+  }
+}
+</script>
+
+## Card
+
+### Install
+``` javascript
+import { Card } from 'vant';
+
+Vue.component(Card.name, Card);
+```
+
+### Usage
+
+#### Basic Usage
+
+:::demo Basic Usage
+```html
+<van-card
+  title="Title"
+  desc="Description"
+  num="2"
+  price="2.00"
+  :thumb="imageURL"
+/>
+```
+:::
+
+#### Advanced Usage
+Use `slot` to custom content.
+
+:::demo Advanced Usage
+```html
+<van-card
+  title="Title"
+  desc="Description"  
+  num="2"
+  price="2.00"
+  :thumb="imageURL"
+>
+  <div slot="footer">
+    <van-button size="mini">Button</van-button>
+    <van-button size="mini">Button</van-button>
+  </div>
+</van-card>
+```
+:::
+
+### API
+
+| Attribute | Description | Type | Default | Accepted Values |
+|-----------|-----------|-----------|-------------|-------------|
+| thumb | Left thumb | `String` | - | - |
+| title | Title | `String` | - | - |
+| desc | Description | `String` | - | - |
+| num | Number of goods | `String | Number` | - | - |
+| price | Price of goods | `String | Number` | - | - |
+| centered | Whether content vertical centered | `String` | `false` | - |
+
+### Slot
+
+| name | Description |
+|-----------|-----------|
+| title | Custom title |
+| desc | Custom description |
+| tags | Custom tags |
+| thumb | Custom thumb |
+| footer | Custom footer |