docs: refine document format

Picked from:
9735dfe

Author: marjune163

README.md

@@ -12,7 +12,7 @@ Simple command line based HTTP file server to share local file system.
 - Can specify a custom theme for page rendering
 - Support location alias(mount another directory to url location)
 
-# Tech Features
+## Tech Features
 - Monolithic architecture
 - Stateless
 - Zero third party dependency

README.zh-CN.md

@@ -12,7 +12,7 @@
 - 可以指定自定义主题来渲染页面
 - 支持目录别名（将另一个目录挂载到某个URL路径）
 
-# 技术特色
+## 技术特色
 - 单体架构
 - 无状态
 - 零第三方依赖