feat: improve type arguments for Snippet and $bindable

[NotWoods]

When looking at the type for Snippet (for example, using Go to Type Definition in VSCode) it's difficult to tell what generics to pass. I replaced the vauge T name with Arguments and added some JSDoc. I also fixed the sample code for Snippet to use a tuple.

Additional small change in the same vein: rename t in $bindable to fallback in the types

Svelte 5 rewrite

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[changeset-bot]

🦋 Changeset detected

Latest commit: e02b505

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! Can you run pnpm generate:types from packages/svelte and commit the change? Then we're good to go

[Rich-Harris]

thank you!