chore: prep release workflow for `@next` release

[huntabyte]

This PR adds the next branch to the release.yml workflow so that it is in place. We can soon do a prerelease @next for the Svelte 5 version testing/usage prior to a full merge/release into main.

I'll create the next branch from the existing forked branch I have in this project and move those changes into it. I currently have @next deployments going for bits-ui, form snap, and paneforge, and changesets make it stupidly simple!

[changeset-bot[bot]]

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Latest commit: 0c32c4ad6f4422ce55b1b2dacf41204c966ba0be

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Name	Status	Preview	Comments	Updated (UTC)
svelte-sonner	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Oct 6, 2024 11:19pm

[huntabyte]

This is good to merge into main @wobsoriano. Won't have any impact but we need it in main to kick off the next release workflows when the time comes 😃

Planning to give the next branch another look and come up with some API ideas for the stuff we don't yet have a solution for (component vs function for the promise toast) and hopefully, we can get an next release rolling to catch any bugs before eventually making it the main release.

[wobsoriano]

Thanks @huntabyte! Learning a lot off changeset + versioning stuff with these updates