replace react with preact

[proddy]

Inspired by rjwats/esp8266-react#327 I thought I'd have another go at trying out preact. preact is a lightweight version of react, with a much smaller bundle size and ideal for slow connections where loading speed could be a problem. There are drawbacks obviously (see https://www.merixstudio.com/blog/what-preact-and-when-should-you-consider-using-it) but for our project, I think it's safe and worth experimenting with.

Using the compatibility mode (preact/compat) and the vite plugin preact/preset-vite I only needed to replace react() with preact() in the vite.config.ts.

It saves 36KB in Flash so now we're able to use the espressif IDF4.4.4/pio 6.3.2 library on an 2MB ESP32. Pretty impressive for changing one line.

Thanks @rjjrbatarao :-)