%23%23 Description

This PR introduces comprehensive documentation (`nextjs-mf-sharing-diagram.md`) to clarify the Next.js Module Federation plugin's internal sharing mechanisms. It explains *why* Next.js 14 and 15 share similarly (primarily differing by server vs. client environment, not version) and details the prepared layer-based sharing for Next.js 15. This helps users understand the plugin's behavior and future capabilities.

Additionally, it includes a bug fix to prevent unwanted build configuration files (like `.swcrc`) from being published to npm, which was causing Jest test failures. A minor typo in the Next.js documentation has also been corrected.

%23%23 Related Issue

- Fixes %233873
- Addresses a user request for detailed documentation on Next.js Module Federation sharing internals.

%23%23 Types of changes

- [x] Docs change / refactoring / dependency upgrade
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)

%23%23 Checklist

- [ ] I have added tests to cover my changes.
- [x] All new and existing tests passed.
- [x] I have updated the documentation.