[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/nav-bar.vue

@@ -0,0 +1,18 @@
+<template>
+  <demo-section>
+    <demo-block :title="$t('basicUsage')">
+      <van-nav-bar
+        :title="$t('title')"
+        :leftText="$t('back')"
+        :rightText="$t('button')"
+        leftArrow
+      />
+    </demo-block>
+
+    <demo-block :title="$t('advancedUsage')">
+      <van-nav-bar :title="$t('title')" :leftText="$t('back')" leftArrow>
+        <van-icon name="search" slot="right" />
+      </van-nav-bar>
+    </demo-block>
+  </demo-section>
+</template>