Added timestamps in ExampleSettingsSeeder

```
action@freelance-80648:~/workspace/your-project-name$ php artisan db:seed --class="Davzie\LaravelBootstrap\Seeds\DatabaseSeeder"                                                                                                    
User Table Seeded                                                                                                                                                                                                                   
Seeded: Davzie\LaravelBootstrap\Seeds\ExampleUserSeeder                                                                                                                                                                             
                                                                                                                                                                                                                                    
                                                                                                                                                                                                                                    
                                                                                                                                                                                                                                    
  [Illuminate\Database\QueryException]                                                                                                                                                                                              
  SQLSTATE[23000]: Integrity constraint violation: 19 settings.created_at may not be NULL (SQL: insert into "settings" ("key", "label", "value") values (application_name, Application Name, Savico CMS))                           
                                                                                                                                                                                                                                    
                                                                                                                                                                                                                                    
                                                                                                                                                                                                                                    
db:seed [--class[="..."]] [--database[="..."]]                                                                                                                                                                                      
                                                                                                                                                                                                                                    ```