Update the documentation

[lf94]

I think the documentation needs to separate itself from FindETH (it's ok to mention it), and needs a blurb about how to extend it and use it.

I'll provide a PR.

[Mrtenz]

I'm not sure what you mean by separating it from FindETH? The current documentation is just auto-generated with Typedoc. I agree that the documentation can be improved a lot though, and this is something I will work on in the future.