feat: 添加 README，更新 .gitignore，移除 JE-Skin/eskin-finger-sdk

- 添加 README.md 项目文档
- 更新 .gitignore 排除 JE-Skin/、eskin-finger-sdk/ 及构建产物
- 从 git 跟踪中移除 JE-Skin 和 eskin-finger-sdk

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/serial_core/error.rs

@@ -48,4 +48,4 @@ impl fmt::Display for CodecError {
     }
 }
 
-impl std::error::Error for CodecError {}
+impl std::error::Error for CodecError {}