Attach library to a specific page
If you're using a twig template, you can add it there. 

{{ attach_library('module/library') }}


Which is helpful when you want to control whether the library loads before or after the content.

https://www.drupal.org/docs/8/theming-drupal-8/adding-stylesheets-css-and-javascript-js-to-a-drupal-8-theme