gh-proxy 仅下载模式

本代理只支持文件下载，不支持浏览 GitHub 网页。

完整链接模式：
  https://你的域名/https://github.com/user/repo/archive/refs/heads/main.zip
  https://你的域名/https://raw.githubusercontent.com/user/repo/main/file.txt

标准路径模式：
  https://你的域名/user/repo/raw/main/file.txt
  https://你的域名/user/repo/archive/refs/heads/main.zip
  https://你的域名/user/repo/releases/download/v1.0/app.zip

git clone：
  git clone https://你的域名/user/repo.git