Add documentation to code and readme

[simzzz]

I find the project really useful, the stack is very good for making scalable projects easily. It took some time however to get the hang of it since I'm not very experienced with nest. I think it will help other users start their projects right away with some sort of documentation similar to https://github.com/sahat/hackathon-starter

[bojidaryovchev]

Thanks for the feedback! I shall get on it as soon as I got time