docs: add Picture-in-picture mode screenshot

Author: JuneLin2001

README.md

@@ -51,9 +51,16 @@
 
 ## Screenshots
 
+### 3D scenes
 ![Scene](./screenshots/685wGIF.gif)
+
+### Pomodoro Timer and Todo List
 ![Timer](./screenshots/Timer.gif)
 
+### Picture-in-picture mode
+![Picture-in-picture](./screenshots/pipGIF.gif)
+
+
 ## Run Locally
 
 ```bash

docs/README_zh-TW.md

@@ -45,9 +45,16 @@
 
 ## 網站截圖
 
+### 3D 場景
 ![Scene](./../screenshots/685wGIF.gif)
+
+### 番茄鐘與 Todo List
 ![Timer](./../screenshots/Timer.gif)
 
+### 子母畫面模式
+![Picture-in-picture](./../screenshots/pipGIF.gif)
+
+
 ## 本地運行
 
 ```bash