Add timezone selector, alarm, stopwatch, timer, theme toggle and impr…

[DaniyalMusadiq1]

Description

This PR significantly enhances the original clock app by adding multiple new features, a modern glass‑morphism UI, and full responsiveness. It also updates the README to reflect the new capabilities.

✨ New Features

• Real‑time Clock – Smooth second updates using requestAnimationFrame.
• Date Display – Shows weekday, month, day, and year.
• 12/24 Hour Format Toggle – Switch between 12‑hour (with AM/PM) and 24‑hour formats.
• Timezone Selector – Choose from:
  • Local time
  • UTC
  • New York (America/New_York)
  • London (Europe/London)
  • Tokyo (Asia/Tokyo)
  • Pakistan (Asia/Karachi)
• Alarm – Set a one‑time alarm; triggers a browser notification and a beep sound.
• Stopwatch – Start, pause, record lap times, and reset.
• Timer – Set a countdown timer (minutes & seconds) with pause/reset and notification on finish.
• Theme Switcher – Toggle between light and dark modes (default dark). Preference saved in localStorage.
• Fully Responsive – Exactly one screen height, no scrolling – works perfectly on mobile, tablet, and desktop.
• Settings Persistence – Format, timezone, and theme choices are remembered.

🎨 UI/UX Improvements

• Redesigned with a clean glass‑morphism look.
• Smooth transitions and hover effects.
• Improved layout that adapts to any screen size.

📚 Documentation

• Updated README.md with a detailed Features section to showcase all new additions.
• Kept the original contribution guide intact.

✅ How to Test

1. Open the app – the current time and date should display.
2. Change the format and timezone – the clock updates immediately.
3. Set an alarm and wait for it to trigger (notification + sound).
4. Use the stopwatch (start, lap, reset).
5. Set a timer and let it count down.
6. Toggle the theme and refresh – your preference is saved.

📸 Screenshots

💬 Additional Context
This PR builds on the original app by AvidCoder101 and adds modern functionality while keeping the code beginner‑friendly. All changes are fully commented.

[AvidCoder101]

@DaniyalMusadiq1 This is amazing! Thanks so much for your contributions