A snippet which will show an input prompt that you can inject the library from the cdn to the current website for debugging

bookmarklet.txt

javascript:(function(){var a=prompt("Enter the url: ","//cdnjs.cloudflare.com/ajax/libs/jquery/1.9.1/jquery.min.js");if(a.length>0){var b=document.createElement("script"),c=document.getElementsByTagName("script")[0];b.src=a,c.parentNode.insertBefore(b,c)}})();

debug_insert.js

(function(){
    var url = prompt ('Enter the url: ', '//cdnjs.cloudflare.com/ajax/libs/jquery/1.9.1/jquery.min.js');
    if(url.length > 0) {
        var script = document.createElement('script');
        var firstScript = document.getElementsByTagName('script')[0];
        script.src = url;
        firstScript.parentNode.insertBefore(script, firstScript);
    }
}());