chore: fix template repo updater

[AdrianGonz97]

closes #243

• Removed the postpublish script and moved the updater to its own workflow step
• Added a check to only commit new files when the working tree is dirty
• Template repo's commit message now references the sv version

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Latest commit: cc9ec6c

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[pkg-pr-new]

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pnpm add https://pkg.pr.new/sveltejs/cli/sv@246

commit: cc9ec6c

[manuel3108]

Like the changes, although i don't think there is a way to test this without just merging it? If there isn't feel free to merge.