Registering Custom Javascript Libraries in Azure Mobile Services

I was excited how easy it is to use SendGrid in Azure Mobile Services Server Side Scripts.

Here's what I mean: http://www.windowsazure.com/en-us/develop/mobile/tutorials/send-email-with-sendgrid/

The interesting part is, that a developer can call new SendGrid() after adding the add-on.

var sendgrid =newSendGrid('**username**','**password**');

Now, I would like to register a custom library for our developers to use through AMS Server Side Scripts. Say, I want them to be able to call var smsgateway = new SmsGateway('**username**', '**password**); and have my own implementation in the custom registered library.

How could I accomplish this?