Add Routing to the user and admin 'dapp'

[JasoonS]

Here is a little article on routing: https://blog.minima.app/posts/2020/reasonml-safe-routing

I would say stop at the Using different types for matching and navigation section. IMO it makes the code more complex without too much benefit - yes it is more 'type-safe' but routing isn't really one of the places where I'm too worried about using strings and spelling things wrong probably isn't likely anyway.

It is in reason syntax, but I'm sure you'll be fine converting it now that you've done some rescript.

https://reasonml.github.io/reason-react/docs/en/router.html