[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/dialog.md

@@ -0,0 +1,63 @@
+## Dialog
+
+### Install
+
+```js
+import { Dialog } from 'vant';
+```
+
+### Usage
+
+#### Alert dialog
+Used to prompt for some messages, only including one confirm button
+
+```javascript
+Dialog.alert({
+  title: 'Title',
+  message: 'Content'
+}).then(() => {
+  // on close
+});
+
+Dialog.alert({
+  message: 'Content'
+}).then(() => {
+  // on close
+});
+```
+
+#### Confirm dialog
+Used to confirm some messages, including a confirm button and a cancel button
+
+```javascript
+ Dialog.confirm({
+  title: 'Title',
+  message: 'Content'
+}).then(() => {
+  // on confirm
+}).catch(() => {
+  // on cancel
+});
+```
+
+### Methods
+
+| Name | Attribute | Return value | Description |
+|-----------|-----------|-----------|-------------|
+| Dialog.alert | options | `Promise` | Show alert dialog |
+| Dialog.confirm | options | `Promise` | Show confim dialog |
+| Dialog.close | - | `void` | Close dialog |
+
+### Options
+
+| Attribute | Description | Type | Default | Accepted Values |
+|-----------|-----------|-----------|-------------|-------------|
+| title | Title | `String` | - | - |
+| message | Message | `String` | - | - |
+| showConfirmButton | Whether to show confirm button | `Boolean` |  `true` | - |
+| showCancelButton | Whether to show cancel button | `Boolean` |  `false` | - |
+| confirmButtonText | Confirm button text | `String` |  `Confirm` | - |
+| cancelButtonText | Cancel button test | `String` | `Cancel` | - |
+| overlay | Whether to show overlay | `Boolean` | `true` | - |
+| closeOnClickOverlay | Whether to close when click overlay | `Boolean` | `false` | - |
+| lockOnScroll | Whether to lock body scroll | `Boolean` | `true` | - |