DOC: Update README.md with latest app screenshots.

### Issue with current README:

The **README.md** contains outdated app screenshots of Theme Screen (Vintage) that don't match with the latest update.

Issues:
- Outdated Attachment: The app screen attached for Theme Screen is outdated and needs to be updated.

Proposed Fix:
- Update the attachment with latest screenshot.

Preview:
-

@M4dhav Can this issue be assigned to me? I have a the update ready to submit.