docs: add download instructions for each system in the readme

Co-authored-by: twostraws <paul.hudson@gmail.com>

Author: 2 people

README.md

@@ -10,6 +10,27 @@ Make sure git is installed on your computer.
 
 Download the application, open it, and let your creativity flow! Generating a repository may take a while. After generation, copy the repository folder and enter it to continue.
 
+### Windows/Linux
+
+Download and run the application directly.
+
+### macOS
+
+Since this application is not yet signed, you may encounter security restrictions on first launch. Follow these steps to resolve:
+
+```bash
+cd the-directory-where-green-wall.app-is-located
+sudo xattr -cr ./green-wall.app
+sudo spctl --master-disable
+sudo xattr -r -d com.apple.quarantine ./green-wall.app
+```
+
+**Tip:** You don't need to execute all of these commands. Try them in order from top to bottom, and stop once one resolves the issue.
+
+**Warning:** The commands will not automatically launch the application. You need to manually double-click the app to start it (the commands only modify file attributes).
+
+### Quick Tips
+
 - Right-clicking during the painting process can switch between the brush and the eraser.
 
 ## Next steps

README_zh.md

@@ -10,6 +10,27 @@
 
 下载软件，打开，发挥你的艺术才能！生成仓库需要等待一会，生成后复制仓库目录进入仓库文件夹。
 
+### Windows/Linux
+
+下载后直接点击运行即可。
+
+### macOS
+
+由于本应用暂时未进行签名服务，首次运行时可能会遇到安全限制。按以下步骤解决：
+
+```bash
+cd 你的green-wall.app存在的目录
+sudo xattr -cr ./green-wall.app
+sudo spctl --master-disable
+sudo xattr -r -d com.apple.quarantine ./green-wall.app
+```
+
+**提示：** 这些指令并不需要全部执行，从上往下依次尝试，如果某条指令解决了问题就无需继续执行。
+
+**警告：** 命令执行后不会自动弹出应用界面，需要手动双击应用来启动（命令只是改变了文件属性）。
+
+### 快速提示
+
 - 绘画过程中右键可以切换画笔和橡皮擦
 
 ## 下一步操作