docs(readme): Update readme

Author: anibalsanchez

README.md

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 # Using Guzzle in a WordPress plug-in with PHP-Prefixer
 
-Using Guzzle in a WordPress plug-in with PHP-Prefixer
+**Using prefixed Guzzle with PHP-Prefixer** plug-in for WordPress. A plug-in to showcase the PHP-Prefixer service and how to use Guzzle in the WordPress Ecosystem.
+
+## About the Plugin
+
+A plug-in to integrate Guzzle, PHP HTTP client, in a WordPress plug-in with PHP-Prefixer. The plug-in shows a number fact from numbersapi.com using Guzzle as HTTP client. It is inspired by the Hello Dolly plug-in.
+
+## About PHP-Prefixer
+
+It’s super quick to get a [PHP-Prefixer](https://php-prefixer.com/) project up and running. Install any library freely. PHP-Prefixer will manage your namespaces.
+
+- **Use the same libraries across all platforms**: Develop your solutions using the same libraries for all the platforms you work in, specifically WordPress, Joomla, Drupal, Laravel, Symfony, Slim Framework, etc.
+- **Composer + WordPress**: Use Composer for your WordPress projects. PHP-Prefixer will process the dependencies to run smoothly along with other third-party plug-ins.
+- **Fully integrated with Git**: Declare your name space configuration and let the service produce the packages. No local installation. No Phars. No new dependencies.
+
+## About Guzzle, PHP HTTP client
+
+Guzzle is a PHP HTTP client that makes it easy to send HTTP requests and trivial to integrate with web services. For more information, please, visit <https://docs.guzzlephp.org/en/stable/index.html>
+
+
+## References
+
+- Blog: [New Tutorial: Using PHP Composer in the WordPress Ecosystem](https://blog.php-prefixer.com/2020/10/23/new-tutorial-using-php-composer-in-the-wordpress-ecosystem/)
+- Documentation: [How to Prefix a WordPress Plugin](https://php-prefixer.com/docs/guides/how-to-prefix-wordpress-plugin/)
+
+## License
+
+MIT License
+
+## Copyright
+
+Copyright (c) 2021 Desarrollos Inteligentes Virtuales, SL