chore: brew install mysql v9 (#713)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Documentation**
- Updated setup instructions to reflect the requirement for MySQL 9,
removing references to MySQL 5.7 and 8.
- Removed outdated troubleshooting information related to MySQL 8
authentication issues.

- **Chores**
- Updated `.gitignore` to include `.egg/` and improved formatting for
`.DS_Store`.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.gitignore

@@ -120,3 +120,5 @@ dist
 .DS_Store
 run
 !test/ctx_register.js
+
+.egg/

docs/setup.md

@@ -21,38 +21,11 @@ $ docker-compose down
 
 假设大家使用 macOS 开发，Linux 和 Windows 环境自行参考。
 
-### MySQL 5.7
+### MySQL 9
 
 ```bash
-$ brew install [email protected]
-$ brew services start mysql
-```
-
-### MySQL 8
-
-```bash
-$ brew install mysql
-$ brew services start mysql
-```
-
-如果遇到以下异常
-
-```log
-Uncaught Error: ER_NOT_SUPPORTED_AUTH_MODE: Client does not support authentication protocol requested by server; consider upgrading MySQL client
-```
-
-需要先确认安装的 MySQL 版本，如果是 8.x，在执行时可能会报错不支持此种鉴权方式，需要改一下 MySQL 设置
-
-```bash
-# 登录数据库
-mysql -u root
-
-> use mysql;
-> update user set plugin='mysql_native_password' where user='root';
-> quit;
-
-# 重启 MySQL
-brew services restart mysql
+brew install mysql
+brew services start mysql
 ```
 
 ### Redis