Image preview frame in new window

[aaronsnoswell]

Hello!

First off, thanks for this awesome tool. I'm a game designer and I've recently been using HCCD, but this tool seems to offer a few features that HCCD doesn't.

I'm currently running cardpen locally and it occurred to me that this would be a lot nicer to use if the card preview could be 'popped out' into a new window. I know you can do this with HTML as I've coded it before (a long time ago).

If you point me to the relevant parts of the codebase I'm happy to try implementing this myself and submit a PR!

Thanks!