Add frontend and backend integration example

This MR adds an example component that interacts with the backend. This can serve as an example of how to integrate with the rest (pun intended) of the app.

This is what the example component looks like:

I think we should also scope all backend routes to /api. This wouldn't require any change from the backend, but when deploying, we just need to make sure that the base url for the backend is "https://csclub.uwaterloo.ca/links/api". I also updated the client-server integration diagram to reflect this change. Here's the diagram:

CC @n3parikh for the backend change