feat: add Snippet type

[dummdidumm]

Intended usage is something like this:

let { banner } = $props<{ banner: Snippet<boolean> }>();

Language tools will adjust its output to type all snippets as a Snippet<..> variable, which guards against people passing in regular functions to snippet props.

related to #9447

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Name	Status	Preview	Comments	Updated (UTC)
svelte-5-preview	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 21, 2023 2:19pm

[aradalvand]

@dummdidumm Is there a reason the Snippet type doesn't allow more than a single parameter? Isn't that a bit of an arbitrary limitation?

[dummdidumm]

Because only one parameter is allowed due to how code generation works. You can use destructuring to get the same result as having multiple arguments. It's also consistent with $props that way which might refactoring a bit easier if you decide to turn a snippet into a comment.