Updated README.md

This is mostly a straight copy from the EE3 README.

I'm not sure how the `libs` part is supposed to work, so do tell me if I did something wrong :).
About the odd formatting near the end of `Compiling Block Extenders`, that's because Markdown is stupid and automatically assumes that I want to start a new list...

Also, in order for anybody to access your wiki, you have to click on it first :wink:.