feat: Add standards verification document and examples for city-timez…

…ones-go

- Created STANDARDS_VERIFICATION.md to outline compliance with GitHub markdown standards and industry best practices.
- Added examples/README.md to provide practical usage examples for the city-timezones-go library.
- Introduced examples/cli/usage.sh for demonstrating command-line tool usage.
- Enhanced caching mechanism in internal/city/cache.go with LRU eviction and statistics tracking.
- Removed limits.go and limits_test.go as they were deemed unnecessary.
- Updated public API in pkg/citytimezones to include cache management functions.
- Added comprehensive tests for cache functionality in pkg/citytimezones/citytimezones_test.go.

Enhance README.md with comprehensive documentation updates

- Added a detailed Table of Contents for easier navigation.
- Expanded the Features section to highlight performance and memory efficiency.
- Included a new "Why Choose This Library?" section outlining key advantages.
- Added performance comparison metrics and benchmarks for clarity.
- Updated the Contributing section with clearer steps and a Development Setup guide.
- Introduced new sections for Documentation, Support, Related Projects, Acknowledgments, and License for better organization.