feat: add new asset images and update README with visuals

Author: euxx

.github/assets/actions.gif

@@ -18,6 +18,11 @@
 - ✨ Clean, minimal UI — feature-rich without the clutter
 - 🎨 Light / Dark / System theme with adjustable popup width
 
+| | |
+|---|---|
+| <img src=".github/assets/notifications.png" alt="Notifications" width="400"> | <img src=".github/assets/actions.gif" alt="Actions" width="400"> |
+| <img src=".github/assets/signin.png" alt="Sign in" width="400"> | <img src=".github/assets/settings.png" alt="Settings" width="400"> |
+
 ## Usage
 
 1. **OAuth (recommended)** — Click "Sign in with GitHub", enter the code on GitHub