fix: use Vite by default for Svelte and Vue

[benmccann]

What I did

New Vue and Svelte projects use Vite by default. Those ecosystems are heavily invested in Vite and promote it as the default builder. If someone were creating a component library that didn't need a builder, we'd want them to use Vite with Storybook since that's what most of the users will be using and what we'd be most equipped to provide help with

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]

[IanVS]

Looks good, thanks. I have two minor suggestions to consider.