user_restrictions.local_actions.yml

user_restrictions_create_form:
  route_name: user_restrictions.create_form
  title: 'Add rule'
  appears_on:
    - user_restrictions.list_form

user_restrictions.menu_links.yml

user_restrictions.list_form:
  title: 'User Restrictions'
  parent: user.admin_index
  description: 'Specify rules for restricted usernames and e-mail addresses.'
  weight: -5
  route_name: user_restrictions.list_form

user_restrictions.routing.yml

user_restrictions.list_form:
  path: '/admin/config/people/user-restrictions'
  defaults:
    _form: '\Drupal\user_restrictions\Form\UserRestrictionsListForm'
    _title: 'User Restrictions'
  requirements:
    _permission: 'administer user restrictions'

user_restrictions.create_form:
  path: '/admin/config/people/user-restrictions/add'
  defaults:
    _form: '\Drupal\user_restrictions\Form\UserRestrictionsAddForm'
  requirements:
    _permission: 'administer user restrictions'