[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/search.md

@@ -0,0 +1,76 @@
+## Search
+
+### Install
+``` javascript
+import { Search } from 'vant';
+
+Vue.component(Search.name, Search);
+```
+
+### Usage
+
+#### Basic Usage
+
+```html
+<van-search placeholder="Placeholder" v-model="value" />
+```
+
+```javascript
+export default {
+  data() {
+    value: ''
+  }
+}
+```
+
+#### Listen to Events
+`search` event will be triggered when click the search button on the keyboard.
+
+`cancel` event will be triggered when click the cancel button.
+
+Tips: There will be a search button on the keyboard when Search is inside a form in iOS.
+
+```html
+<form action="/">
+  <van-search
+    v-model="value"
+    placeholder="Placeholder"
+    :showAction="true"
+    @search="onSearch"
+    @cancel="onCancel">
+  </van-search>
+</form>
+```
+
+#### Custom Button
+Use `action` slot to custom right button, `cancel` event will no longer be triggered when use this slot
+
+```html
+<van-search
+  v-model="value"
+  :showAction="true"
+  @search="onSearch">
+  <div slot="action" @click="onSearch">Search</div>
+</van-search>
+```
+
+### API
+
+| Attribute | Description | Type | Default | Accepted Values |
+|-----------|-----------|-----------|-------------|-------------|
+| placeholder | Input placeholder | `String` | - | - |
+| background | Background color | `String` | `#f2f2f2` | - |
+| showAction | Whether to show right button | `Boolean` | false | - |
+
+### Event
+
+| Event | Description | Attribute |
+|-----------|-----------|-----------|
+| cancel | Triggered when click cancel button | - |
+| search | Triggered when confirm search | - |
+
+### Slot
+
+| name | Description |
+|-----------|-----------|
+| action | Custom right button, displayed when `showAction` is true |