simple_styleguide.routing.yml

simple_styleguide.controller:
  path: '/simple-styleguide'
  defaults:
    _controller: '\Drupal\simple_styleguide\Controller\DefaultController::index'
    _title: 'Simple Styleguide'
  requirements:
    _permission: 'access style guide'

simple_styleguide.configuration_panel:
  path: '/admin/config/styleguide'
  defaults:
    _controller: '\Drupal\system\Controller\SystemController::systemAdminMenuBlockPage'
    _title: 'Styleguide'
  requirements:
    _permission: 'administer site configuration'

simple_styleguide.styleguide_settings:
  path: '/admin/config/styleguide/settings'
  defaults:
    _form: '\Drupal\simple_styleguide\Form\StyleguideSettings'
    _title: 'Settings'
  requirements:
    _permission: 'administer site configuration'
  options:
    _admin_route: TRUE