added js files via processwire $config

adding js files via processwire $config allows us to add extra js files as needed for each template file. if a certain content type (e.g. 'playlist') needs a certain js file (e.g. 'audio.js'), then we add $config->scripts->add($config->urls->templates . 'js/audio.js'); in the template file so it is only loaded for pages with that template/content type.