Docs: add performace testing to docs/README.md (#40)

Author: chhy2009

docs/README.md

@@ -4,6 +4,7 @@ English | [中文](README.zh_CN.md)
 * [Quick Start](./en/quick_start.md)
 * [Basic Tutorial](./en/basic_tutorial.md)
 * [Architecture Design](./en/architecture_design.md)
+* [Performance testing](./en/benchmark.md)
 * User Guide:
   * [Compile & Install](./en/setup_env.md)
   * [Proto Management](./en/proto_management.md)

docs/README.zh_CN.md

@@ -4,6 +4,7 @@
 * [快速入门](./zh/quick_start.md)
 * [基础教程](./zh/basic_tutorial.md)
 * [架构设计](./zh/architecture_design.md)
+* [性能测试](./zh/benchmark.md)
 * 用户指南:
   * [环境搭建](./zh/setup_env.md)
   * [Proto文件依赖管理](./zh/proto_management.md)