Include full image size in reference list

[JoryHogeveen]

https://wordpress.org/support/topic/template-image-url-for-full-size/

Related GitHub issue(s)

Fixes #7183

Changelog text for these changes

PR checklist

• I have tested my own code to confirm it works as I intended.
• My code follows the WordPress Coding Standards.
• My code follows the WordPress Inline Documentation Standards.
• My code includes automated tests for PHP and/or JS (if applicable).

[what-the-diff]

PR Summary

• Enhancement of Image Configuration Options
  The function responsible for managing your website's media content (images, videos) has been updated. Now, there's an additional image size option, named 'full', that allows utilization of images in their original size. This means you can now display your images without any automatic cropping or resizing, providing more flexibility in presenting visual content.