[docs] update homepage CTA

[benmccann]

The CTA right now it's a bit split between "Read the introductory blog post to learn more." and "npm create svelte@latest my-app". The blog post is two years old and talks quite a bit about Sapper, the code being private, Snowpack, etc. so it feels rather outdated

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[Conduitry]

two years old

Oh, fuck, it is, isn't it? Crazy.