Pre-JS loading state

[edd]

If you are on a slow connection, or fetching the trading app via IPFS, it can take a long time to load. Which is fair - it's a pretty big bundle. But while it's loading in all the JS, all you see is a blank white page.

Previously there was a loading indicator in the HTML that was replaced at app startup

Tasks

• [ ] Have some loading state that can render with few/no external assets, as soon as the HTML is loaded