export to JSON

[zkat]

We should have a simplified JSON format that holds page metadata in JSON, and renders each note into html, mechanics blocks and character sheets and everything.

There should probably be two modes: one where blocks are rendered as html, and one where they're rendered as static images using the current theme, with something like html2canvas and inlining data: URIs.

This format will be much more useful for folks who want to publish their campaigns in static site generators or things like substack, while still taking advantage of nice block rendering.

This is probably going to be heavily based on the Webpage HTML Export plugin, but we need things to be a bit more bespoke than what that plugin can output.