Document disadvantages of React context

[japgolly]

And specifically address those considering using it to avoid plumbing args. Include alternate solutions and examples of techniques that arg plumbing easier seeing as it's a common practice with scalajs-react.

[japgolly]

Context hooks may mitigate some of the problems with using React context

  const locale = useContext(LocaleContext);
  const theme = useContext(ThemeContext);