Serialize elm-ui to json

[bburdette]

Feature request, not a bug!

I've been thinking about writing a proof-of-concept rust executable that would run elm in the deno engine. Instead of providing a DOM, the rust program would receive a serialized elm-ui structure, parse it, and render it using a rust UI toolkit. So elm-ui straight to UI without converting to html first.

What's missing is the ability to serialize elm-ui structs (to json, probably). I could just fork elm-ui since its just a proof-of-concept, but thought I'd at least put the idea out there.