Use PostCSS + Webpack

[iafan]

When rebuilding parts of the UI in React, we want to take advantage of the locally-scoped CSS rules tied to React components, and this use this as an opportunity to clean up monolithic CSS we currently have.

Let's use PostCSS for this and integrate it with Webpack so that we can produce final CSS bundles upon saving individual component CSS files.

[julen]

Also worth considering: https://styled-components.com/

[iafan]

Also worth considering: https://styled-components.com/

I'm ok with styled components as well. Let's pick something (e.g. styled components) and try to build some of the new components with it. Then will see if we need to re-evaluate the approach.