feat: add output flag with Destination interface.

Added -o flag to write results to files using a new Destination interface.

Changes:
- Add Destination interface with StdoutDestination and FileDestination implementations.
- Add -o flag to CLI parser for output file specification.
- Update Config to use Destination instead of direct output handling.
- Refactor main to use Destination.Write() for result output.

internal/config/parse_from_args.go

@@ -13,6 +13,7 @@ func FromArgs() (*Config, error) {
 	statistics := flag.Bool("s", false, "Statistics. If set, the process will print various statistics about the run.")
 	profile := flag.String("p", "", "CPU profiling. If an output file is defined, the program will profile its execution and dump its results into it.")
 	file := flag.String("f", "", "File. If set, read source from the specified file.")
+	output := flag.String("o", "", "Output. If set, write result to the specified file. Use '-' for stdout (default).")
 	flag.Parse()
 
 	// Parse source type.
@@ -36,8 +37,17 @@ func FromArgs() (*Config, error) {
 		}
 	}
 
+	// Parse destination type.
+	var destination Destination
+	if *output == "" || *output == "-" {
+		destination = StdoutDestination{}
+	} else {
+		destination = FileDestination{Path: *output}
+	}
+
 	return &Config{
 		Source:      source,
+		Destination: destination,
 		Verbose:     *verbose,
 		Explanation: *explanation,
 		Profile:     *profile,