File block: Allow content only editing

[talldan]

What?

See #65778

Allows contentOnly editing in the file block.

How?

Adds role: content to the file block attributes. I've tried to match other media blocks like image with the attributes that receive the content role.

Testing Instructions

1. Open a template in the Site Editor
2. Insert a file block in one of the sections
3. Switch to Write mode
4. Try editing the file block

Screenshots or screencast

Before

Kapture.2024-10-01.at.14.59.03.mp4

After

Kapture.2024-10-01.at.15.01.26.mp4

[github-actions]

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Co-authored-by: talldan <[email protected]>
Co-authored-by: andrewserong <[email protected]>

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[andrewserong]

Good catch, this is all testing nicely for me!

✅ Confirmed that before, the File block cannot be interacted with in Write / contentOnly mode when it's part of a section in a template
✅ With this applied, I can upload a file, and update its filename text and download button text

LGTM! 🚀