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/codec.rs

@@ -4,4 +4,4 @@ use std::time::Instant;
 pub trait Codec<F> {
     fn decode(&mut self, input: &[u8], session_started_at: Instant) -> Result<Vec<F>, CodecError>;
     fn encode(&self, frame: &F) -> Result<Vec<u8>, CodecError>;
-}
+}