Documentation: Describe supported scoring systems (with visual examples?)

It would be helpful to have a section in the docs with a bit of a blurb on each of the supported scoring systems to help users figure out which one they want to use. Some graphical representations of the targets would be even better.

Not going to sign up to implement this one as I'd like to get #56 squared off and then I need to focus back on archr for a while, but its probably not urgent.

Start by locating the project documentation and the code or entry points that define the supported scoring systems. Document each supported system with a short explanation and add graphical target examples if the existing documentation structure supports them. Done means users can compare the systems and choose one, with the documentation changes rendered or checked as appropriate.

Written by the indexing model from the issue text.