Move to NextJS

[nightzirch]

The reason for moving over to Vercel's NextJS is primarily due to performance, SEO and simplicity. With NextJS's most recent v10 release, the support for internationalization, server-rendered images and more, the project have lots of opportunities to grow in the future.

The move isn't without complications though. We will need to do a bunch of rewriting and phasing out of the current global state library ReactN in favor of Vercel's own SWR. Turns out we can make ReactN work with NextJS, so we'll keep that in as to not scope this release too ambitiously.

To do:

• [X] Get rid of ReactN in favor of SWR
• [X] Rewrite pages to work with NextJS
• [x] Rewrite the auth and session state
• [X] Move some API calls to server-side Moving this to a task of its own.

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[nightzirch]

The code is still far from optimized considering I want to phase out Reactn in favor of contexts and SWR, but that will require a bigger backend rewrite, so I will leave it for now.

This PR is also not without errors, but those will be fixed in other PRs and tasks. This PR was primarily to rewrite to NextJS, and that has been done. It will build and deploy to Vercel, and that's pretty cool.