[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/image-preview.md

@@ -0,0 +1,32 @@
+## ImagePreview
+
+### Install
+
+```js
+import { ImagePreview } from 'vant';
+```
+
+### Usage
+
+#### Basic Usage
+
+```javascript
+ImagePreview([
+  'https://img.yzcdn.cn/1.jpg',
+  'https://img.yzcdn.cn/2.jpg'
+]);
+```
+
+#### Custom Start Position
+```javascript
+ImagePreview([
+  'https://img.yzcdn.cn/1.jpg',
+  'https://img.yzcdn.cn/2.jpg'
+], 1);
+```
+
+### Arguments
+
+| Attribute | Description | Type |
+|-----------|-----------|-----------|
+| imageUrls | Image URL list | `Array` |