Include-test-extension is a project mainly written in JavaScript, it's free.
test extension for simple include() method to add js or css files from the Opera extension package to popup.html or options.html
This extension exists to show how you can include .js and .css files in your options.html or popup.html from within the extension package
include({js: '/path/to.js'})
include({js: ['/path/one.js', '/path/two.js'], css: '/path/to.css'})