Allow SSR with MacawUI

[krzysztofzuraw]

We currently have a naive way of rendering MacawUI - we apply CSS variables on the client. As a proper solution, we should apply them in SSR as well.

Relevant code

macaw-ui/src/theme/context.tsx

Line 25 in 8d3da0c

setElementVars(document.documentElement, vars, themes[theme]);