Use `@vseth/components` component library

The current plan is to use the VSETH component library located at https://gitlab.ethz.ch/vseth/0403-isg/sip-infrastructure/vseth-frontend. This could be a step that could help other ETH student associations use community-solutions instead of a custom exam collection. Until VIS develops its own theme I will use the vseth-theme which we can modify slightly until a proper theme can be used. it shouldn't be too hard to integrate dark-mode as well in such a custom theme using css-variables and the react context API.