Add uix demo

[elken]

Add a demo for https://github.com/pitch-io/uix per discussion on slack

I wasn't able to start this up locally due to datomic, but I've tested the main code on the xtdb-starter and all functions as expected 😄

Don't know if this codebase is also subject to the same agreement as the main electric repo; if that's the case let me know on slack and I'll sign it 😄

[dustingetz]

Thanks. No CA needed here. We will merge when we get a chance.

[elken]

Great! No rush

[ggeoffrey]

We are deprecating this repo and moving demos to Electric Fiddle.
I’ll copy your PR there and mention you so we can keep track of it.