docs: add banner.txt support documentation

- Add comprehensive banner.txt usage documentation to README.md and README_en.md
- Document variable substitution support in banner.txt
- Include examples of compiled output with banner
- Resolves #2: 增加对banner.txt的支持

The banner.txt feature was already implemented in webpack.common.js but lacked documentation.
Users can now add ASCII art or decorative text that gets inserted as comments in compiled userscripts.

Author: CC11001100

README.md

@@ -118,6 +118,42 @@ npm install
 
 ![image-20230817004653299](README.assets/image-20230817004653299.png)
 
+## Banner支持
+
+项目支持在编译后的代码中添加自定义banner。在项目根目录的`banner.txt`文件中，你可以添加ASCII艺术字或其他装饰性文本：
+
+```
+▗▄▄▄▖▗▖  ▗▖▗▄▄▖ ▗▄▄▄▖ ▗▄▄▖ ▗▄▄▖▗▄▄▖ ▗▄▄▄▖▗▄▄▖▗▄▄▄▖
+  █   ▝▚▞▘ ▐▌ ▐▌▐▌   ▐▌   ▐▌   ▐▌ ▐▌  █  ▐▌ ▐▌ █
+  █    ▐▌  ▐▛▀▘ ▐▛▀▀▘ ▝▀▚▖▐▌   ▐▛▀▚▖  █  ▐▛▀▘  █
+  █    ▐▌  ▐▌   ▐▙▄▄▖▗▄▄▞▘▝▚▄▄▖▐▌ ▐▌▗▄█▄▖▐▌    █
+```
+
+编译时，banner内容会被自动插入到油猴脚本头部注释中，支持以下变量替换：
+- `${name}` - 项目名称
+- `${version}` - 版本号
+- `${description}` - 项目描述
+- `${author}` - 作者信息
+- `${repository}` - 仓库地址
+- `${namespace}` - 命名空间
+- `${document}` - 文档地址
+
+编译后的效果：
+```javascript
+// ==UserScript==
+// @name         my-project
+// @version      1.0.0
+// ...
+// ==/UserScript==
+
+//    ▗▄▄▄▖▗▖  ▗▖▗▄▄▖ ▗▄▄▄▖ ▗▄▄▖ ▗▄▄▖▗▄▄▖ ▗▄▄▄▖▗▄▄▖▗▄▄▄▖
+//      █   ▝▚▞▘ ▐▌ ▐▌▐▌   ▐▌   ▐▌   ▐▌ ▐▌  █  ▐▌ ▐▌ █
+//      █    ▐▌  ▐▛▀▘ ▐▛▀▀▘ ▝▀▚▖▐▌   ▐▛▀▚▖  █  ▐▛▀▘  █
+//      █    ▐▌  ▐▌   ▐▙▄▄▖▗▄▄▞▘▝▚▄▄▖▐▌ ▐▌▗▄█▄▖▐▌    █
+
+// 你的代码...
+```
+
 然后就可以开心的写代码了，在编写代码的时候你可以使用`npm`命令为项目添加依赖，对于一个稍微复杂点的脚本而言很可能会引用外部的依赖：
 
 ```bash

README_en.md

@@ -131,6 +131,42 @@ In addition to variable substitution, all other content will be preserved as is,
 
 ![image-20230817004653299](README.assets/image-20230817004653299.png)
 
+## Banner Support
+
+The project supports adding custom banners to the compiled code. In the `banner.txt` file in the project root directory, you can add ASCII art or other decorative text:
+
+```
+▗▄▄▄▖▗▖  ▗▖▗▄▄▖ ▗▄▄▄▖ ▗▄▄▖ ▗▄▄▖▗▄▄▖ ▗▄▄▄▖▗▄▄▖▗▄▄▄▖
+  █   ▝▚▞▘ ▐▌ ▐▌▐▌   ▐▌   ▐▌   ▐▌ ▐▌  █  ▐▌ ▐▌ █
+  █    ▐▌  ▐▛▀▘ ▐▛▀▀▘ ▝▀▚▖▐▌   ▐▛▀▚▖  █  ▐▛▀▘  █
+  █    ▐▌  ▐▌   ▐▙▄▄▖▗▄▄▞▘▝▚▄▄▖▐▌ ▐▌▗▄█▄▖▐▌    █
+```
+
+During compilation, the banner content will be automatically inserted into the userscript header comments, supporting the following variable substitutions:
+- `${name}` - Project name
+- `${version}` - Version number
+- `${description}` - Project description
+- `${author}` - Author information
+- `${repository}` - Repository address
+- `${namespace}` - Namespace
+- `${document}` - Document address
+
+Compiled result:
+```javascript
+// ==UserScript==
+// @name         my-project
+// @version      1.0.0
+// ...
+// ==/UserScript==
+
+//    ▗▄▄▄▖▗▖  ▗▖▗▄▄▖ ▗▄▄▄▖ ▗▄▄▖ ▗▄▄▖▗▄▄▖ ▗▄▄▄▖▗▄▄▖▗▄▄▄▖
+//      █   ▝▚▞▘ ▐▌ ▐▌▐▌   ▐▌   ▐▌   ▐▌ ▐▌  █  ▐▌ ▐▌ █
+//      █    ▐▌  ▐▛▀▘ ▐▛▀▀▘ ▝▀▚▖▐▌   ▐▛▀▚▖  █  ▐▛▀▘  █
+//      █    ▐▌  ▐▌   ▐▙▄▄▖▗▄▄▞▘▝▚▄▄▖▐▌ ▐▌▗▄█▄▖▐▌    █
+
+// Your code...
+```
+
 Then you can happily start coding. While writing code, you can use the `npm` command to add dependencies to your project. For a slightly more complex script, it is very likely to reference external dependencies:
 
 ```bash