OBGM-345 Upgrade to Webpack 5
- Replace OptimizeCSSAssetsPlugin with CssMinimizerPlugin
- Use `options` block instead of `?key=value&…` notation
- Update all webpack dependencies to latest versions
- Update babel to latest 7.x release
- Bump ESLint to latest version
- Bump sass and jest to latest versions
- Remove react-styleguidist dependency, which I don’t think we use
- Resolve *all* known node security warnings, except for `react-localize-redux`
