feat: add self-closing-tags migration

[dummdidumm]

Companion to sveltejs/svelte#11114. This adds an npx svelte-migrate self-closing-tags migration that replaces all the self-closing non-void elements in your .svelte files.

Alternative to #12102 with the following adjustments:

• doesn't migrate slots that are not real custom element slots (will make diff much less noisy)
• doesn't migrate when namespace is foreign
• leaves tag-like strings inside scripts/styles etc alone

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Latest commit: 4a5b9ec

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svelte-migrate	Minor

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[Rich-Harris]

ideally this would work on Svelte 5 codebases too (which means having svelte@next as a dependency, and using walk from either estree-walker or zimmerframe instead of svelte/compiler)

Suggested change

	'<script lang="ts">let a: string = ""</script><div></div>'
	'<script lang="ts">let a: string = ""</script><div></div>',
	'{#snippet foo()}<div />{/snippet}': '{#snippet foo()}<div></div>{/snippet}'

[dummdidumm]

This should work in Svelte 5 code bases, too, because when you do npx .. aren't you storing the whole dependenies in a isolated folder somewhere on your computer? If not then yes we can switch to zimmerframe.

Oh wait I see what you mean. Mhhhhm how does npx work in general in these situations? Can it pick up dependencies from the environment it's run in? If so then we can do await import('svelte') and use that.

[dummdidumm]

Using the local Svelte installation now, tested it successfully on the Svelte 5 repo