Added styling and custom alert to Age Calculator

[Nikitakandwal]

Fixes Issue🛠️

Closes #569

Description👨‍💻

1. Added animation styles to Age Calculator title.
2. Set a default valid age to avoid any errors in the first go.
3. Added custom alerts
4. Added alerts for negative age too.
5. Added shadows and hover styling to main container for age calculator
6. Added a favicon for Age Calculator page

Type of change📄

• New feature (non-breaking change which adds functionality)

How this has been tested✅

Edge Web Browser and Chrome Browser on local machine.

Checklist✅

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added demonstration in the form of GIF/video file
• I am an Open Source Contributor

Screenshots/GIF📷

[netlify]

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[github-actions]

Hey @Nikitakandwal, Welcome to the project CalcDiverse! 🎊
Thanks for your contribution! Your effort makes this project better. Keep it up! 🙌
Please wait for the PR to be reviewed. Happy Coding!! ✨

[Rakesh9100]

Merged, Congrats on getting your PR merged to this repo under SWOC S4 🎉🎉 @Nikitakandwal