fix init command in starter app on about page

[Conduitry]

The about page on the create-svelte template said npx init svelte@next rather than npm init svelte@next. It also apparently hadn't been formatted correctly by Prettier when it was last saved. I'm torn about whether this should include a subdirectory to create, like we're doing elsewhere in the docs. Maybe?

Changesets are currently messed up, so for now one is not included in here. This package is called ~TODO~ as far as changesets can tell. I've manually edited the included changeset file and will try to look into what's going on here separately.

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• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
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• Ideally, include a test that fails without this PR but passes with it.

Tests

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