Docs: add English language support (#170)

* feat: support lang entry build

* feat: vant support lang switch

* move lang iframe-router to utils & fix router link bug

* add en-US config && add some translation

* chang async. to async_ (support superman cdn)

* add layout translation

* change nav style

* upgrade zan-doc

* fix: doc config

* upgrade zan-doc && remove useless code

* fix changelog generate path

build/build-changelog.sh

@@ -17,4 +17,4 @@ github_changelog_generator \
   --issues-label "**处理的 Issue:**" \
   --pr-label "**合并的 Pull Request (可能有不兼容改动):**" \
   --no-unreleased \
-  -o $basepath/../docs/examples-docs/changelog-generated.md
+  -o $basepath/../docs/examples-docs/zh-CN/changelog-generated.md