Suggestion: Clearer installation docs

[dhndmn]

After trying to use shadcn-svelte@next for a Svelte 5 component, I struggled with various errors for days when implementing in an app. I finally realized that my issue was not the code but that the app had the current package of bits-ui instead of bits-ui@next. If a reminder to also update the bits-ui package were in the installation steps, it would save people like me a lot of headache. Maybe it should have been obvious, but it didn't cross my mind until far too long.