docs: update YouTube Music Background Play README

- Expand feature description to include background browser support
- Add Browser Support section with Safari compatibility info
- Remove iOS Safari limitation (now supported)
- Reorganize screenshot to end of document for better readability

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: rxliuli

src/plugins/youtube-music-background-play/README.md

@@ -1,12 +1,20 @@
 # YouTube Music Background Play
 
-A userscript that prevents YouTube Music from pausing playback when running in background tabs.
+A userscript that prevents YouTube Music from pausing playback when switching tabs or running the browser in the background.
 
 ## What it does
 
-This userscript intercepts browser APIs that YouTube uses to detect if you're actively watching, allowing music to continue playing when you switch to other tabs.
+This userscript intercepts browser APIs that YouTube uses to detect if you're actively watching, allowing music to continue playing when you:
 
-<img width="590" height="1280" alt="image" src="https://github.com/user-attachments/assets/c2bf18d7-fbdc-486f-9b68-5f0e3e966b3d" />
+- Switch to other tabs
+- Minimize the browser window
+- Switch to other applications
+
+## Browser Support
+
+- ✅ Chrome/Edge/Firefox - Full support
+- ✅ macOS Safari - Full support (requires Tampermonkey or Userscripts extension)
+- ✅ iOS Safari - Full support (requires Userscripts extension)
 
 ## Installation
 
@@ -17,7 +25,6 @@ This userscript intercepts browser APIs that YouTube uses to detect if you're ac
 
 - **Unstable**: YouTube may update their detection methods at any time, causing this userscript to stop working
 - **Computer sleep**: Playback will still pause when your computer goes to sleep or hibernates
-- **iOS Safari**: This userscript does not work on iOS Safari due to platform-specific restrictions
 - **Updates**: May break when YouTube updates their site
 
 ## How it works
@@ -33,6 +40,10 @@ The userscript overrides the following browser APIs:
 
 This userscript is for personal use. Use at your own risk.
 
+## Screenshot
+
+<img width="590" height="1280" alt="iOS Safari Screenshot" src="https://github.com/user-attachments/assets/c2bf18d7-fbdc-486f-9b68-5f0e3e966b3d" />
+
 ## Discord
 
 Join the discussion: <https://discord.gg/C2baQRZUCW>