docs: enhance dynamic-remotes example documentation

Update README with comprehensive documentation covering:
- Architecture overview and dynamic loading patterns
- Setup instructions for both Rspack and Webpack
- Key Module Federation concepts demonstrated
- Known issues and modernization roadmap
- Best practices and troubleshooting guide

Addresses critical documentation gaps and provides clear path
for updating outdated dependencies and configurations.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: ScriptedAlchemy