Add Logging & Debugging Support

[Aha43]

For debugging purposes, it would be useful to:

• Log when a handler is discovered.
• Log when a command matches or fails to match.

🔹 Improvement Suggestion: Add a ILogger (from Microsoft.Extensions.Logging) and allow users to enable logging.

Modify Spf constructor:

private readonly ILogger<Spf> _logger;

public Spf(string[] args, IServiceCollection services, string baseNamespace = "", ILogger<Spf>? logger = null)
{
    _logger = logger ?? NullLogger<Spf>.Instance;
    _baseNamespace = baseNamespace.ToLower();
    var serviceProvider = services.BuildServiceProvider();
    _serviceProvider = serviceProvider;
    _handlers = DiscoverHandlers(serviceProvider);
    _exitor = serviceProvider.GetService<ISpfExitor>();
    _noMatchHandler = serviceProvider.GetService<ISpfNoPromptMatchHandler>();
}