feat: add fetchpriority to image attrs

[ascorbic]

This is a version of #10388 for Svelte 4

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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• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• Prefix your PR title with feat:, fix:, chore:, or docs:.
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

[changeset-bot]

🦋 Changeset detected

Latest commit: c2ca4f6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

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svelte	Patch

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[dummdidumm]

Thank you!