docs: update sample code

Spark command is recommended.

Author: kenjis

user_guide_src/source/cli/cli_library/001.php

@@ -1,11 +1,16 @@
 <?php
 
-namespace App\Controllers;
+namespace App\Commands;
 
+use CodeIgniter\CLI\BaseCommand;
 use CodeIgniter\CLI\CLI;
-use CodeIgniter\Controller;
 
-class MyController extends Controller
+class MyCommand extends BaseCommand
 {
     // ...
+
+    public function run(array $params)
+    {
+        // ...
+    }
 }