Update README.md with table of contents

[T-Fathima]

What does this PR do?

This PR introduces improvements to the Table of Contents section in the README to enhance readability and accessibility, centering the section and adding updated links for easier navigation.

Fixes #306

Type of change

• Chore (refactoring code, technical debt, workflow improvements)
• Documentation update (README, inline comments, etc.)

How should this be tested?

• Verify that the Table of Contents is centered in the README when viewed on GitHub.
• Check that each link in the Table of Contents directs to the correct section in the document.

Mandatory Tasks

• Make sure you have self-reviewed the code. A decent size PR without self-review might be rejected.

@swarooppatilx Please review and merge my code under gssoc-ext and hacktoberfest

[vercel]

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[github-actions]

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