Add comprehensive examples and validation features to Configurator

• Created EXAMPLES.md with various configuration examples including basic usage, web server configuration, environment variable overrides, validation, and JSON support.
• Updated README.md to reflect new features and installation instructions.
• Added a sample JSON configuration file (config.json) for demonstration.
• Implemented a new Validator module with constraints for numeric comparisons, range checks, non-empty strings, and regex pattern matching.
• Developed extensive unit tests for configuration access and validation functionalities.
• Enhanced test coverage for various scenarios including nested configurations and type preservation.