Show media file sizes in Media Library grid view

[wprashed]

Summary

Displays attachment file sizes in the Media Library grid view.

Why

File size is useful when reviewing media because it helps site owners and developers identify oversized images and improve performance awareness without opening each attachment's details panel.

Changes

• Adds file size to grid attachment labels when filesizeHumanReadable is available.
• Shows file size beneath filenames for non-image grid items.
• Includes file size in the grid item's accessible label, which also makes it visible in the existing image thumbnail label overlay.
• Adds light styling for the file-size text in filename overlays.

Testing

• php -l src/wp-includes/media-template.php
• vendor/bin/phpcs --standard=phpcs.xml.dist --runtime-set testVersion 7.4- src/wp-includes/media-template.php
• node --check src/js/media/views/attachment.js
• git diff --check

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Props wprashed.

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[github-actions]

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