[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/demos/views/button.vue

@@ -0,0 +1,92 @@
+<template>
+  <demo-section>
+    <demo-block :title="$t('title1')">
+      <van-button type="default">Default</van-button>
+      <van-button type="primary">Primary</van-button>
+      <van-button type="danger">Danger</van-button>
+    </demo-block>
+    
+    <demo-block :title="$t('title2')">
+      <van-button size="large">Large</van-button>
+      <van-button size="normal">Normal</van-button>
+      <van-button size="small">Small</van-button>
+      <van-button size="mini">Mini</van-button>
+    </demo-block>
+
+    <demo-block :title="$t('disabled')">
+      <van-button disabled>Diabled</van-button>
+    </demo-block>
+
+    <demo-block :title="$t('title3')">
+      <van-button loading></van-button>
+      <van-button loading type="primary"></van-button>
+    </demo-block>
+
+    <demo-block :title="$t('title4')">
+      <van-button tag="a" href="https://www.youzan.com" target="_blank">
+        {{ $t('button') }}
+      </van-button>
+    </demo-block>
+
+    <demo-block :title="$t('title5')">
+      <van-button type="primary" bottomAction>{{ $t('button') }}</van-button>
+
+      <van-row>
+        <van-col span="12">
+          <van-button bottomAction>{{ $t('button') }}</van-button>
+        </van-col>
+        <van-col span="12">
+          <van-button type="primary" bottomAction>{{ $t('button') }}</van-button>
+        </van-col>
+      </van-row>
+    </demo-block>
+  </demo-section>
+</template>
+
+<script>
+export default {
+  i18n: {
+    'zh-CN': {
+      title1: '按钮类型',
+      title2: '按钮尺寸',
+      title3: '加载状态',
+      title4: '自定义按钮标签',
+      title5: '页面底部操作按钮'
+    },
+    'en-US': {
+      title1: 'Type',
+      title2: 'Size',
+      title3: 'Loading',
+      title4: 'Custom Tag',
+      title5: 'Action Button'
+    }
+  }
+}
+</script>
+
+
+<style lang="postcss">
+.demo-button {
+  .van-button {
+    user-select: none;
+
+    &--large,
+    &--bottom-action {
+      margin-bottom: 15px;
+    }
+
+    &--small,
+    &--normal {
+      margin-right: 10px;
+    }
+  }
+
+  .van-doc-demo-block {
+    padding: 0 15px;
+  }
+
+  .van-doc-demo-block__title {
+    padding-left: 0;
+  }
+}
+</style>