add hook to open a URL

The problem: I want bitmask JS UI to be able to open links in a new browser window. I can't do this in javascript, because it will try to open a new window in the current browser, which might not work if it is running in embedded widget (or worse, might replace the bitmask ui).

Instead, I want the ability to open a new window in a browser using the operating system's preferred method. This could be added to bitmask.js API, so that the backend can just pass the url to the OS, or it could be a hook exposed to the UI js by the wrapper application.