Previously, assets (images and fonts) hosted on squonk.informaticsmatter.org were used. Although this worked ok there were several issues with this method.

• It required settings cors policies correctly on the squonk-website deployment at squonk.informaticsmatter.org which has gone wrong in the past
• A white labelled version of the app would be accessing assets on our domain
• It is trickier to optimize these assets in Next.js. We have to whitelist the domain for image optimization

This PR brings the assets into a local folder via a Git subtree to a new repo. The images are then directly accessed using the NextJS Image tag, which has optimization benefits. The fonts are now loaded locally with the next/font module rather than our SASS loader. This allows us to remove the dependency on SASS entirely. It, additionally, can bring some optimizations via the next/font library to reduce bad behaviours like layout shift.