[new feature] add i18n support (#310)

* fix: Tabbar icon line-height

* [new feature] progress add showPivot prop

* [new feature] TabItem support vue-router

* [new feature] update document header style

* [Doc] add toast english ducoment

* [new feature] add i18n support

* feat: Extract demos from markdown

* feat: Base components demos

* [new feature] complete demo extract & translate

* [fix] text cases

* fix: add deepAssign test cases

* fix: changelog detail

* [new feature] AddressEdit support i18n

docs/markdown/en-US/switch-cell.md

@@ -0,0 +1,64 @@
+## SwitchCell
+`SwitchCell` component is an encapsulation of `Switch` and `Cell`.
+
+### Install
+``` javascript
+import { SwitchCell } from 'vant';
+
+Vue.component(SwitchCell.name, SwitchCell);
+```
+
+### Usage
+
+#### Basic Usage
+
+```html
+<van-cell-group>
+  <van-switch-cell v-model="checked" title="Title" />
+</van-cell-group>
+```
+
+```javascript
+export default {
+  data() {
+    return {
+      checked: true
+    }
+  }
+}
+```
+
+
+#### Disabled
+use `disabled` property to disable the component
+
+```html
+<van-cell-group>
+  <van-switch-cell v-model="checked" disabled title="Title" />
+</van-cell-group>
+```
+
+
+#### Loading
+use `loading` property to keep component in loading state
+
+```html
+<van-cell-group>
+  <van-switch-cell v-model="checked" loading title="Title" />
+</van-cell-group>
+```
+
+### API
+
+| Attribute | Description | Type | Default | Accepted Values |
+|-----------|-----------|-----------|-------------|-------------|
+| v-model | on-off state of the switch | `Boolean` | - | - |
+| title | the leftside title |  `String` | `''` | - |
+| loading | whether the component is in loading state |  `Boolean` | `false` | - |
+| disabled | whether to disable the component |  `Boolean` | `false` | - |
+
+### Event
+
+| Event | Description | Attribute |
+|-----------|-----------|-----------|
+| change | triggered when the on-off state is changed | checked: switch is on or not |