How to create a custom page programmatically in Drupal 8

name: CodimTh Controller
description: Create a custom page in drupal 8
package: CodimTh
type: module
core: 8.x

codimth.content:
  path: '/hello'
  defaults:
    _controller: '\Drupal\codimth_controller\Controller\CodimthController::index'
    _title: 'Create a custom page in drupal 8!'
  requirements:
    _permission: 'access content'

<?php
namespace Drupal\codimth_controller\Controller;
use Drupal\Core\Controller\ControllerBase;

class CodimthController extends ControllerBase
{
    public function index()
    {
        return array(
            '#type' => 'markup',
            '#markup' => $this->t('Welcome to codimth.com !'),);
    }
}