Docs: Use dynamic Vite imports in snippets

[JReinhold]

Reacts to #26291 (comment)

What I did

Changed all imports from of Vite in main.ts documentation to be dynamic imports, to minimize the risk that users get a warning about Vite CJS bundles being deprecated.

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  MIGRATION.MD

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  • bug: Internal changes that fixes incorrect behavior.
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[kylegach]

Seems good to me!

Should we include a comment about why the dynamic import is necessary? I trust your judgement there.