by Klaylton Fernando on WordPress.org
Add CSS and Javascript to your pages simply and quickly. WP Custom Code supports CodeMirror.

The fields will be printed on posts and pages.
This plugin adds 3 fields on every page and blog post where you can type your code in a readable interface.
In addition to being very light and functional, the WP Custom Code plugin also allows you to work with external libraries. Basque paste the address
of the javascript library of your choice in the designated field and you will be able to enjoy this indispensable resource.