Upgrade readme

[masteradhoc]

What?

Updates readme.md to improve the structure and content of the plugin's documentation header.

Why?

The previous readme lacked a banner image, proper badge organization, and a ## Description section. This improves the first-impression presentation of the plugin.

How?

• Adds a WordPress.org banner image at the top of the readme
• Reorganizes badge links (Test, Deploy, WordPress Playground Demo) into a cleaner layout
• Adds PHP version, WordPress version, tested-up-to, and license badge shields
• Adds WP.org Rating, Downloads, and Active Installs badge shields
• Adds a ## Description section explaining that the plugin adds a second form of authentication to protect against unauthorized access even if passwords are compromised

Testing Instructions

1. View readme.md on GitHub or in a Markdown previewer
2. Verify the changes

Screenshots or screencast

Old Header:

New Header:

Changelog Entry

Changed - Improved readme.md structure with banner image, reorganized badges, and a dedicated Description section.

[github-actions]

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Co-authored-by: masteradhoc <masteradhoc@git.wordpress.org>

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