feat: add fetchpriority to img attrs

[ascorbic]

This PR adds the fetchpriority attribute to HTML attributes. This has been requested in #8099, which was rejected as an experimental feature. It is now implemented in Chromium and Safari, and is in the WhatWG spec.

I am the maintainer of @unpic/svelte (recommended in the docs ), and currently need to add it as an augmented property. It would be good if we could add it instead.

Fixes #8099

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[dummdidumm]

Yeah makes sense to add it now 👍
This is the Svelte 5 branch, can you open a similar one for the svelte-4 branch?

[ascorbic]

@dummdidumm done in #10390!