Fix vulnerabilities

So npm install doesn't complain anymore (and less vulnerability and stuff i guess).

Just FYI, stuff has been updated, most notably webpack, from 3.12.0 to 4.16.1. Stuff starts to break with a version higher than 4.16.1 (somethingsomething os-locale).

Following warnings are new:

WARNING in configuration
The 'mode' option has not been set, webpack will fallback to 'production' for this value. Set 'mode' option to 'development' or 'production' to enable defaults for each environment.
You can also set it to 'none' to disable any default behavior. Learn more: https://webpack.js.org/concepts/mode/

WARNING in asset size limit: The following asset(s) exceed the recommended size limit (244 KiB).
This can impact web performance.
Assets: 
  amiv/kultur.png (2.21 MiB)
  bundle.js (6.13 MiB)

WARNING in entrypoint size limit: The following entrypoint(s) combined asset size exceeds the recommended limit (244 KiB). This can impact web performance.
Entrypoints:
  main (6.13 MiB)
      bundle.js


WARNING in webpack performance recommendations: 
You can limit the size of your bundles by using import() or require.ensure to lazy load some parts of your application.
For more info visit https://webpack.js.org/guides/code-splitting/

With webpack@4.16.2 or higher it starts becoming an error. Somebody smarter than me can figure it out.