Remove redux in favour of React context

[robbieaverill]

We probably don't need to use Redux anymore, we can use the React context API instead.

Next.js have an official example of how to use Redux in Next: https://github.com/vercel/next.js/tree/canary/examples/with-redux

Objectives:

• Server side logic (if applicable) only fetches data that it needs for that request, since "On the server side every request initializes a new store, because otherwise different user data can be mixed up. On the client side the same store is used, even between page changes.
• Client side pages share state and do not need to re-fetch user information, cart, etc unless they explicit want to do so
• Statically generated pages work