[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/number-keyboard.md

@@ -0,0 +1,69 @@
+## NumberKeyboard
+
+### Install
+``` javascript
+import { NumberKeyboard } from 'vant';
+
+Vue.component(NumberKeyboard.name, NumberKeyboard);
+```
+
+### Usage
+
+#### Basic Usage
+
+```html
+<van-button @touchstart.native.stop="showKeyboard = true">
+  Show Keyboard
+</van-button>
+
+<van-button @touchstart.native.stop="showKeyboard = false">
+  Hide Keyboard
+</van-button>
+
+<van-number-keyboard
+  :show="showKeyboard"
+  @blur="showKeyboard = false"
+  @input="onInput"
+  @delete="onDelete"
+/>
+```
+
+```javascript
+export default {
+  data() {
+    return {
+      showKeyboard: true
+    }
+  },
+
+  methods: {
+    onInput(value) {
+      Toast(value);
+    },
+    onDelete() {
+      Toast('delete');
+    }
+  }
+}
+```
+
+### API
+
+| Attribute | Description | Type | Default | Accepted Values |
+|-----------|-----------|-----------|-------------|-------------|
+| show | Whether to show keyboard | `Boolean` | - | - |
+| title | Keyboard title | `String` | - | - |
+| extraKey | Content of bottom left key | `String` | `''` | - |
+| zIndex | Keyboard z-index | `Number` | `100` | - |
+| transition | Whether to show transition animation | `Boolean` | `true` | - |
+| showDeleteKey | Whether to show delete button | `Boolean` | `true` | - |
+
+### Event
+
+| Event | Description | Attribute |
+|-----------|-----------|-----------|
+| input | Triggered when keydown | key: Content of the key |
+| delete | Triggered when press delete key | - |
+| blur | Triggered when blur keyboard | - |
+| show | Triggered when keyboard is fully displayed. | - |
+| hide | Triggered when keyboard is fully hidden. | - |