Update _sidebar.md

docs/guide/_sidebar.md

@@ -9,6 +9,7 @@
   - [<span class="iconfont icon-router"></span> 开始使用](guide/begin.md)
      - [<span class="iconfont icon-crown"></span> 事前准备](guide/begin#beginner-事前准备)
      - [<span class="iconfont icon-matrix"></span> 登录后台](guide/begin#computer-登录后台)
+     - [<span class="iconfont icon-control"></span> API接口](/api/README)
   - [<span class="iconfont icon-alert"></span> 贡献捐赠](guide/contribute.md)
   - [<span class="iconfont icon-discord"></span> 加入讨论](guide/discuss.md)
   - [<span class="iconfont icon-nut"></span> 更新日志](CHANGELOG.md)