Add hyperlink to media-upload documentation

[bacoords]

What?

While the link to the media-upload readme file works on GitHub, in the Block Editor handbook it doesn't render as a link: https://developer.wordpress.org/block-editor/reference-guides/packages/packages-media-utils/

Screenshots or screencast

Current screenshot of the handbook:

[bacoords]

@ndiego Can you check this and maybe tag it Developer Documentation if you think it makes sense?

[ndiego]

Thanks Brian, I just approved and restarted the failed test.

[Mamaduka]

Hi, @bacoords

Can you rebase the branch on top of the latest trunk? That should resolve CI failures.

[github-actions]

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