feat: Add svelte/prefer-const rule that excludes reactive variables

[bfanger]

The const declaration creates an immutable reference to a value.
The variable identifier cannot be reassigned.
You should understand const declarations as "create a variable whose identity remains constant"

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/const

The ESLint prefer-const doesn't take into account that Svelte's reactivity system is reassigning reactive variables.
The svelte/prefer-const rule skip variables that are created by runes like $props, $derived, $derived.by, etc.

Companion to the rune-prefer-let rule.

[changeset-bot]

🦋 Changeset detected

Latest commit: 5c29c5c

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

This PR includes changesets to release 1 package

Name	Type
eslint-plugin-svelte	Minor

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[ota-meshi]

Could you please propose the rule in a new issue first?