docs: add web UI demo video

Author: sou350121

README.md

@@ -16,6 +16,10 @@ Track hand movements with a regular webcam, optionally control a WujiHand roboti
 
 - Direct file in repo (download/open): `docs/assets/demo1.mp4`
 
+## Demo (Web UI)
+
+- UI-only demo recording (download/open): `docs/assets/demo2.mp4`
+
 ## Why This Project?
 
 Started out wanting to build a cool-looking hand tracking dashboard with a cyberpunk aesthetic. Later got a WujiHand and added hardware control. Made some optimizations along the way, got latency down to ~50ms.

README_CN.md

@@ -16,6 +16,10 @@
 
 - Repo 内原始文件（下载/打开）：`docs/assets/demo1.mp4`
 
+## Demo（网页界面/UI）
+
+- UI 界面演示录像（下载/打开）：`docs/assets/demo2.mp4`
+
 ## 为什么做这个项目？
 
 一开始是想做一个好看的手部追踪仪表板，赛博朋克风格那种。后来有了 WujiHand 机械手，就顺便加上了控制功能。做的过程中踩了不少坑，也做了一些优化，最终延迟大概在 ~50ms。