Idea for preview: use pandoc compiled to wasm instead of markdown-it.js

[mb21]

Got this idea when seeing asterius, they even have a pandoc demo: https://github.com/tweag/asterius/blob/master/README.md#demos

but not sure about the performance, ease of maintainability etc.

Edit: alternatively, we could try:

• spawning pandoc-server in a separate process and see how bad latency is... using a websocket instead of separate HTTP requests could help, but maybe HTTP/2 is just as good.
• pulldown-cmark compiled to wasm

[ickc]

It would be interesting. Another thing I worry is how the live view update would looks like—if it would be jumping around when the document is updating, etc.