Update dependencies

[eliot-akira]

This pull request updates all dependencies to the latest versions.

It includes a few changes to adapt to: @babel/preset-stage-2 being deprecated (replaced with specific plugins), and minor breaking changes in react-head (HeadCollector -> HeadProvider) and react-icons (name exports).

[markusenglund]

Cool. Just a few issues:

• The layout of icons from the 'react-icons'-library has been messed up.
• css-loader gives error readout in the terminal when running npm run build. This can be fixed by removing the minimize option in the webpack config.