Enhance 'Go further' chapter

[marktani]

Right now we hopefully do a good job in introducing all the different concepts of Relay on their own.
We can improve a lot though in explaining how everything fits together. We discussed a bit on that and a good approach seems to enhance the 'Go further' section to include a section on that topic. Additionally, we could provide a few other examples for applications the reader could now tackle pretty much on his own and test out his new found knowledge.

Help on this topic would be highly appreciated, so don't hesitate to discuss with us in our Slack channel or create a PR 🚀