Live preview

[gavinhenderson]

User story

As a user I want to be able to view a preview of the file as I edit the variables.

Technical

There are two ways to do this, we could shift jsPDF to the front end so it can generate the thumbnails without ever hitting the network. We would have to publish the package to achieve this.

Alternatively we could setup some kind of socket connection (or just poll) to request a preview from the backend. This should be done in a 'lazy' manner so not to slam the backend or block the front end.