Fix with-svelte-example (#6986)
### Description
- vite-plugin-svelte is now a peer dependency and therefore needs to
appear in the user's `package.json`
- fixed preprocessor import in `svelte.config.js`
- removed `optimizeDeps.include` which makes Vite treat the package as
an external dependency that it should bundle once, resulting in changes
not getting picked up (this was introduced in #6576 but I'm not sure
why)
- fixed e2e tests
### Testing Instructions
check manually
Co-authored-by: Anthony Shew <anthony.shew@vercel.com>
