feat: Do not load Previews when the feature is disabled.

[dhnaranjo]

What is the purpose of this pull request?

Avoid loading, for example, test-only gems in production when using sidecar previews. As discussed https://github.com/palkan/view_component-contrib/discussions/24

What changes did you make? (overview)

Added initializer that excludes all files ending in preview.rb in any preview path.

Is there anything you'd like reviewers to focus on?

Nah

Checklist

• [ ] I've added tests for this change
• [x] I've added a Changelog entry
• [ ] I've updated a documentation

[palkan]

Thanks!