Replace react with preact, move instructions to index.html

[incognitojam]

• Move the instructions out of JSX and into index.html
• Simplify the app to mount component in specific div
• Switch to preact which should be a little smaller on bundle size and still gives us preact/hooks for useState, useRef etc. until it is replaced later

Vite is still bundling + hot reloading

Overall this is closer to a plain HTML + JS app, except the fastboot.js logic (basically a state machine) is still written using hooks.